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  • r J >

    Commission of the European Communities



    Report EUR 7937 FR, IT, EN, DE

    Blow-up from microfiche original

  • Commission of the European Communities



    D. AHNER (1), M.A. FARGET (2) (1) CEC - Directorate-General for Agriculture - Brussels (Belgium) (2) I.N.R.A.

    Contract No. 9136


    Directorate-General for Agriculture

    JM EUR 7937 FFI, IT, EN, DE


    Directorate-General Information Market and Innovation

    Btiment Jean Monnet LUXEMBOURG

    LEGAL NOTICE Neither the Commission of the European Communities nor any person

    acting on behalf of the Commission is responsible for the use which might be made, of the following information

    ) ECSC-EEG-EAEC Brussels Luxembourg 1983


    Europe is poor in raw materials, especially energy sources and for this reason its prosperity is bound to suffer in the long term. This trend will not spare farmers; caught between the rising cost of the raw materials they use and the rigidity of the farmgate prices which determine their incomes.

    These difficulties are due to the general economic crisis and in particular the energy crisis; they follow the development boom of the sixties, which conversely, had been spurred on by the very low cost of fuel and power. Agriculture is, however, itself a potential source of energy. Land and water plants have always used solar energy to manufacture products which are at present used mainly to feed and clothe man but which can under certain economic conditions yield energy.

    Of course, the production of food is still the priority for obvious reasons; however, agricultural waste may already provide an appreciable source of energy and the cultivation of certain crops solely for this purpose should be con-sidered/ as should the idea of substituting some agricultural raw materials (timber) for industrial materials which are very costly in terms of energy. This mobilization of the biomass might also be linked with a more efficient use of marginal land7 much of which is not being kept in good heart or is deteriorating because of erosion. The fullert information on the present situation and the future outlook is needed if this new approach for agriculture is to succeed- Our staff has therefore put in hand a study to assess the current situation in this sector-It is in two parts : a bibliographical analysis grouping over a thousand references and a summary with suggestions based on the bibliography. This should help those members of the public interested in this question to a better understanding of the opportunities offered by biomass as a source of renewable energy compared to fossil energy Let us hope that this study will encourage more thought on techniques which could be useful at the present juncture in solving Europe's energy problems

    Claude VILLAIN Director General for Agriculture

  • - II


    This report is chiefly a synthesis of the large number of documents listed in the bibliography. In order to avoid overburdening the text, authors of sources have not been cited each time. This would in any case have made the bibliography redundant.

    Our work is thus more or less a compilation of ideas to be found in the literature, and its main value lies in the attempt to put them into coherent form and to compare and combine the many ideas circulating on the subject in Europe.

    In analysing the literature we have in some cases been led to make additional comments. These have been inserted in the text at points where they would be in context for subsequent discussions.

    Many aspects of the survey have been discussed in depth with research workers and with colleagues in the Commission. We thank them warmly for their help. Our thanks are also due to those of our colleagues who have helped us with the production and publication of this report.

    We hope that this document will give the reader a clear idea of the scope of the subject and promote critical and constructive thinking on it.

    Brussels, May 1981

    Dirk AHNER Marie-Angele PARGET


    Preface I Foreword II Outline of the survey VI

    CHAPTER I: Agriculture and energy ! A. Agriculture as an energy consumer 1 B. Agriculture's energy balance 3 C. The rising cost of energy 8 D. The agricultural sector and the energy crisis 11

    CHAPTER II: Energy biomass - definitions and conversion routes 13 A. Definitions and techniques 13 B. The technical routes for converting biomass into usable energy ...15

    I. Biochemical routes or biological conversion of biomass 15 a) Ethanol production 15 b) Anaerobic digestion 17 c) Aerobic decomposition 20

    II. Thermo-chemical routes 20 a) Combustion 20 b) Pyrolysis 21 c) Gasification 21 d) Methanol production 23 e) Hydrauliquefaction or hydrocracking of cellulose 26

    CHAPTER III: Energy analysis - a new tool for improved interpretation of the 30 allocation of a scarce resource A. General definitions 30

    I. Definition of energy analysis 30 II. Definition of the tools for energy analysis 30 III. Formalization of definitions 31

    B. Problems 34 I. Calculation of input 34

    a) The forms of energy taken into account 34 b) Evaluation of human energy as an input to any 34

    production process c) Calculation of energy flows 34

    II. Calculation of output 35 a) Energy evaluation of output 35 b) Difficulties of calculating output 36 c) The polluting effect of waste material 36

  • - IV

    III. Common measuring standard 36 IV. Energy equivalence coefficients 37 V. Validity of energy analysis in time 38

    C. Energy analysis of waste and energy crops 40

    CHAPTER IV: Biomass - a potential energy source for Europe ? 48

    A. Farm and forest waste 48 I. Availability of waste 48 II. The energy potential of waste 51

    B. Energy crops 54 I. Energy crops: various scenarios 54 II. Energy crops as potential sources of liquid motor fuels 56

    a) Ethanol 56 b) Vegetable oils 57 c ) Methanol 58

    C. Conclusions 59

    CHAPTER V: Use of biomass - some socio-economic considerations 60

    A. Profitability 60 I. The investment needed 60 II. Collection and transport costs 62 III. The cost of producing energy crops 64

    B. Competition for land use 65 I. The problem 65 II. Marginal land and fertile land 65 III. The interdependence of markets 66

    C. Two secondary effects : employment and environment 67 I. Repercussions on employment 67 II. Advantages and disadvantages for the environment 68

    D. The need for a political choice 69 I. Allocation of resources 69 II. Facing the energy crisis 70 III. Biomass in the context of the common agricultural policy (CAP) 71

  • - V -



    International bibliography of the use of biomass for energy I Plan of classification IV A References 1 B. Index of authors 187 C. Index of themes 199 D. Geographic index 205

  • VI


    Agriculture and energy

    1* The remarkable increase in the productivity of agricultural labour in Europe over the last few decades has required a concurrent increase in the direct and indirect consumption of energy by agriculture, now estimated at 5% of total commercial energy consumption in Western Europe.

    2* Following the second oil price shock in 1979/80, the repercussions of the energy crisis on the economic situation of farming have been increasingly felt in Europe, though the consequences have varied widely with the type of production, the structure of production units, regions and countries. The rise in energy prices is therefore liable to affect the competitiveness of regions and to increase income disparities within farming.

    3* If the industry is to adjust to the present energy situation the first priority, as elsewhere, will be to try to save energy. It has been estimated that energy consumption in agriculture could be reduced by 15-20$ if suitable steps were taken.

    In addition, agriculture is particularly well placed to use biomass as a renewable energy source and a partial future replacement for non-renewable fossil fuels. Agriculture would then become an energy producer.

    Energy biomass - definitions and conversion processes

    4* "Biomass" means all organic matter - animal and vegetable - deriving from photosynthesis, by which plants fix their carbon uptake by means of the chlorophyll in their leaves. Even if the photosynthesis yield is low (between 0.4 and 0.8$ a year for most plants), considerable solar energy is fixed in plants each year by this process. Biomass is a renewable energy source but is dispersed and sometimes difficult to tap. In addition, it is not used only to produce energy, since it also serves to satisfy a large number of essential needs (food, shelter, clothing, etc.).

  • - VII -

    5* For these reasons, "energy biomasa" in Europe consists primarily of agricultural and forestry residues and wastes (e.g. straw, manure, brushwood). As well as recovering these by-products it is planned to make limited use of certain plants primarily for energy-producing purposes. The more important of these would be:

    - plants for alcohol production (beet, sorghum, maize, Jerusalem artichoke, etc.);

    - plants yielding oil (colza, sunflower, soya, etc.) which could fuel diesel engines;

    - crops which provide large amounts of dry matter in a short time (short-rotation coppicing, giant reed, etc.).

    Other biomass energy sources are also of interest to Europe: organic waste from the agri-food industries, and urban wastes (household waste, sewage).

    6* At the moment there are two main methods of turning biomass into energy (heat) or fuels: biochemical and thermochemical routes.

    Biochemical routes (biological conversion of biomass) can use wet (i.e., undried) biomass. The main products are: alcohol (ethanol), from fermentation and distillation of sugar-containing juices; methane (in a biogas mixture) produced by anaerobic digestion (e.g. of animal excreta); and direct heat obtained by aerobic digestion.

    Thermochemical processes, however, require relatively dry material (straw, wood) and are carried out at high temperatures. The main products are: direct heat from combustion; charcoal, gas and pyroligneous liquor from pyrolisis; lean gas for heat and power, produced by gasification in gas producers; and methanol (methyl alcohol) synthesized from gas.

    In the case of oil seeds and oleaginous plants, the oil is extracted mechanically, by pressing, or chemically, by means of solvents.

  • VIII

    Energy analysis - Methodology - Interpretation of energy flows

    7* The aim of energy analysis is to calculate the amount of energy necessary, directly or indirectly, to provide a commodity or service (G. Leach's definition). It enables energy balances to be drawn up or energy efficiency (yield) to be calculated. The balance is the outputs less the inputs. Efficiency is the ratio of inputs to outputs in a given system. All data are converted into energy units.

    Energy analysis can be applied both to an entire economy "and to one sector of it (e.g. agriculture) or to a particular form of production. It provides a better interpretation of the forms of energy used and enables energy flows to be estimated. Where biomass energy is concerned, energy analysis is an extremely valuable aid in the choice of conversion processes or in estimating the energy potential of biomass in a given region.

    8* However, energy analysis is a complex technique, and there is some confusion over the definition of the concepts used and how well they are suited to the calculations to be made.

    The number of variables is large - and they may not always be well defined, measurable or be used in a consistent manner. These variables will be reviewed and defined individually. The least controllable element is how to assess inputs in terms of indirect energy.

    All elements necessary for making a comprehensive calculation of energy balances and yields are listed, both for the energy use of residues and waste and for energy crops.

    Biomaas - potential energy for Europe ?

    9* In Community countries, biomass is mainly used for non-energy purposes. In a first phase, therefore, an analysis of biomass availability must concentrate on the wastes or residues of agricultural production.

    Recent studies indicate that about 30-40 million tonnes of oil equivalent toe could be obtained annually by recovering and using farm wastes in the

  • IX -

    Community, say, 2.5 to 3% of the Community's energy consumption forecast for 1985.

    10* As regards potential energy production from energy crops, several scenarios have been worked out for Europe. On fairly conservative assumptions (use of some 7-8 million hectares of "new" land for energy crops) it appears feasible to produce crops corresponding to about 35-40 million toe by the year 2000. This would satisfy about another J>% of the 1985 energy needs forecast for the Community and probably 2.5$ of energy needs in the year 2000.

    Some socio-economic observations

    11* As for any new activity, at the present stage it is difficult to predict production and distribution costs for the use of biomass energy, what shape will be taken by the markets involved and how they will interact with other markets, both those for raw materials and those for end products.

    As harvested biomass is relatively bulky, sometimes highly perishable and generally has a low energy concentration, it must be used near the site of production to avoid prohibitive transport costs. It needs more labour and more complex conversion systems (and so higher investment) than "traditional" fuels (fuel oil, diesel oil, natural gas) to which potential consumers are now accustomed.

    12* Some uses of farm and forest wastes as energy sources at farm or village level are already economically attractive. They could provide some of the energy consumed by agriculture more cheaply than traditional fuels. In contrast, the production of energy crops in the Community is still for the most part at an experimental stage, and in most cases it is not yet certain whether they are economic.

  • - -

    13* The production of energy crops on a large scale would also raise a number of other crucial questions: competition between energy and other uses of biomass; competition for land use; interdependence of markets and security of supply (of energy and food); agricultural restructuring; and risks of soil deterioration.

    14* The use of biomass for energy is one of several possible ways of meeting the challenge of the energy crisis, and - as with the other ways - its development would require sizeable investment. As funds are limited, a political decision will be needed to determine to what extent one solution should be preferred to another.

    Where farm and forest biomass is concerned, the decision coincides with a general discussion on the reform of the common agricultural policy. A crucial point in this discussion is the over-production of certain food products. It may therefore be asked whether a "biomass energy" strategy might not contribute to solving both the over-production problem and the energy problem.

    Naturally, the production of a food product simply for transformation into energy cannot be justified in energy or economic terms. On the other hand, the partial re-allocation of land now producing surpluses to the production of energy could, in the years ahead, be worth careful investigation.

  • Chapter 1



    1. Present-day European agriculture, at least in much of the Community, is often called "modern", "intensive" or "industrial". And the unprecedented increase in the productivity of agricultural labour and land over the last few decades has been mainly brought about by the specialization and intensification of agricultural production, together with major structural changes (decrease in the agricultural working population, increase in the average size of farms). This trend has been dependent on an increase in direct and indirect energy consumption by agriculture. The main indicators are a high degree of mechanization, the intensive use of fertilizers and pesticides, the use of selected seeds and plants, and etockraising with concentrated feedingstuffs.

    2. Many surveys of western agriculture, especially since the 1973/74 energy crisis, show that this trend also brings increasingly clear disadvantages. Two in particular stand out:

    a) The specialization and intensification of agricultural production, with a withdrawal from some less productive agricultural land, and the development of virgin land with consequent erosion, are liable to cause progressive undermining of nature's productive capcitiy.

    b) Agriculture consumes, directly or indirectly, more and more fossil fuel and is thus increasingly dependent on the petroleum products market, where prices have increased more than fivefold in the last ten years. Table 1 illustrates this by comparing the respective consumption of commercial energy per hectare for the production of maize and the corresponding yields in a modern system of agricultural production (USA) and in a traditional agricultural system (Mexico). This commercial energy, even today, is provided almost entirely by fossil fuels.

  • - 2

    In the traditional system, it is used mainly for the production of tools. However, the traditional farmer uses practically no energy for fertilization or seeds, for he does not use chemical fertilizers and his seed has been kept from the previous harvest. The table also clearly shows that yields per hectare in the traditional system are far lower than in the modern system.

    Table 1 Commercial energy needed per hectare for the production of maize by modern methods (USA) and traditional methods (Mexico), with corresponding yields.

    : Machinery : Fuel

    : Chemical : fertilizer

    : Seed

    : Irrigation

    : Pesticides

    : Drying

    : Electricity

    : Transport

    : Total

    : Yield : (kg/ha)

    Modern system (USA)

    Amount per ha

    206 litres

    226.9 kg

    : 20.7 kg

    : 2.2 kg


    Energy ; per ha

    (kg o e)

    100.4 196.9


    : 14.8


    ! 5.2

    : 296

    : 77.6




    Traditional system (Mexico) :

    Amount : per ha

    10.4 kg (a)


    Energy : per ha :

    (kg o e) :

    4.1 :

    4.1 :

    >0 :

    (a) Seed kept from previous year's harvest; commercial energy content is practically zero.

    Source: FAO The state of food and agriculture, 1976, Rome 1977, based on PIMENTEL, D. et al., Pood production and energy crisis, Science, 182, 1975, pp. 445-450.

  • - 3 -

    3 Direct energy uses are mainly to fuel agricultural machinery, heat livestock units and hothouses, and fire driers and desiccators. Indirect uses are chiefly in mineral fertilizer, chemicals (pesticides, herbicides, etc.), certain feedingstuffs and equipment (machinery, tools, buildings, etc.) which need energy to be produced. Figure 1 illustrates this by showing the final energy flows in Denmark's agricultural system in 1974/75

    In Europe, 10-20$ of energy consumption on average is connected with capital invested (i.e. is used in the construction of buildings, machines and other equipment), the rest (80-90$) being consumed in actually running the farms. About half (55-45$) is accounted for by chemical and biological substances (fertilizers and pesticides in particular) and the remaining 45-55$ by direct consumption of fuel and/or electricity.

    Another important factor in the total energy consumption of European agriculture, as the Danish example shows, is the energy content of imported feedingstuffs. For Community farming does not produce all the fodder necessary for its livestock. In 1977/78 about 17$ of Community animal production relied on imported fodder. The percentage varies from 9$ in France to 23$ in Denmark and 53$ in the Netherlands.


    4 The above trends have been accompanied by a deterioration in the marginal energy yield of agriculture, i.e., agricultural production increases at a lower rate than energy consumption once a certain level of intensification is exceeded. This level varies from one crop to another and depends, among other things, on soil and climatic conditions, and on production and rotation systems.

    However, the overall energy balance (agricultural production in energy terms less inputs of commercial energy) is still in surplus: the estimated energy input/output ratio of European agriculture is 1:2.5. This means that

  • Figure 1


    51 Petroleum 509

    164 Electricity 194

    Gas 10

    Buildings 179

    un Equipement


    458 30

    Imported Feed 510

    Source: OECD, Paris. S

    \ ^ V Fodder




    805 !

    235 |

    Sugar beet. 51 1

    Other 211


    Animal products I

    1969 (80%)

    \ r W 355

    < * > Plant products

    388 (15%)


    Horticultural products

    131 (5%)

    Fertilizer ! 637 I

    Machinery ' 298 |

    Chemicals. 18


  • 5

    for the input of one kilocalorie of energy to agricultural production about 2.5 kilocalories of food and feed are produced on average in European farming. If present trends continue the energy input/output ratio is likely to deteriorate further and, for certain crops at least, to fall below parity.

    Already the energy balance is markedly in deficit if the calculation is not confined to agriculture itself but extended to the entire agrifood sector. In the processing, storage and distribution of agricultural products the agrifood industries consume as much, and in some cases considerably more, energy than farming itself. In this context a negative energy balance means that the amount of (scarce) energy needed to put a consumer's daily food on to his plate is much higher than the energy content of the food itself.

    To illustrate this point, Figure 2 shows the commercial energy flow in the French agrifood sector in 1974 It can be seen that for one kilocalorie expended on agricultural production in France, about 2.8 kilocalories of food and feed are produced (input/output ratio: 160:450 = 1:2.8). Accord

    io ing to these calculations, the 300 10 kilocalories used for feeding

    12 livestock give 25 x 10 kilocalories of animal products, a conversion rate of 1 to 12. The consumption of energy in processing, storage and distribution is slightly higher than for the actual agricultural production. In final terms about 5 kilocalories of energy are needed to produce 1 kilocalorie consumed in the human diet.

    The calculation given in Figure 2 is, however, incomplete. We will return to this point later when discussing other energy balances, but it should be noted here that the diagram does not take into account:

    either the commercial energy incorporated in imported feed;

    or the energy content of byproducts and waste which could be used at least partly for nonfood purposes.

  • - 6 -


    Unit = 10IJ kcal


    Harvesting losses

    Losses througn excretion & metabolism

    5J Fertilizer


    Direct con- I sumption of

    fossil fuels various

    Direct-indirect energy

    Loss in food processing & domestic losses Food consumed

    Source: R. Carillon, Etudes du CNEEMA K" 408, L'activit agricole et l'nergie, 1975

    6. When all consumption of commercial energy, direct and indirect, is considered, the greatest energy user in European agriculture is mechanization (for the construction and operation of machinery), followed by the use of mineral fertilizers and, a good way behind, by the use of pesticides and by irrigation. Table 2 shows the estimated amount of energy used in 1972 for each of these purposes in Western European farming, together with corresponding forecasts for 1985/86. Forecasts are based on the assumption that recent trends will continue. In this case there would be a marked increase in the use of fertilizer and a high level of mechanization, which would make farming even more dependent on energy input.

  • - 7 -

    Table 2: Estimated (1972/73) and projection (1985/86) commercial energy-consumption for agricultural production in Western Europe

    : 1.

    : 2.

    : 3-

    : 4.

    : 5-

    Fertilizer a) nitrogen b) phosphates c) potassium

    Mechanisation : a) procurement b) operation ;

    Irrigation ! a) installation : b) operation ;

    Pesticides ;

    Total :

    ! Energy demand in : millions

    : 1972/73

    : 17.29 14.14

    . 2.03 1.12

    31.95 10.9 21.05

    0.37 0.065 0.305



    of toe (1)


    26.99 23.03 2.48 1.48

    39-58 12.35 27.23 !

    0.44 ! 0.07 . 0.37 !

    0.98 :

    67.99 :

    Percentage ' increase increase

    56.1 62.9 18.2 32.1

    23-9 13-3 29-4

    18.9 : 7.2 21.3 :

    12.5 :

    34-7 :

    : % of total demand : : for each

    i 1972/73

    ! 34-3 : 28.0

    4.0 23

    63-3 21.6 41.7

    0.7 . 0.1 0.6



    input :

    : 1985/86 :

    : 39-7 : 33-9 :

    3-6 : 2.2 :

    58.2 : : 18.2 :

    40.0 :

    0.6 : 0.1 : 0.5 :

    1.5 :

    100 : 1 = 2 3 3 = 3

    Source: F.A.O., The state of food agriculture 1976, Rome 1977 (l) toe: tonne of oil equivalent: the calorific value of one tonne of

    petroleum (unit used in comparison and addition of different sources of energy in terms of their equivalent heat content).

    7. Although the energy consumption of agriculture is increasing, its share of total commercial energy consumption is still small compared with that of other sectors, an estimated 5%, in Western Europe and 3.5% world-wide. Table 3 compares consumption in the major regions of the world. It can be seen that in general even if agriculture's energy consumption increases in the future, the effect on total energy demand will be modest.

  • - 8 -

    Table 5; Estimated total commercial energy consumption and commercial energy consumption in agriculture in Western Europe, 1972/73

    B S S K S K B S S E X S a X S S S S S S S S S

    : Developed countries; : North America : Western Europe : Oceania : Others : Developing countries : Africa : Latin America : Near East : Far East

    : Countries with : planned economies


    =======================: Energy consumption, :

    mtoe * :


    3242.7 1838.7 1025.6 58.3 320

    461.7 : 37.5

    194.7 63 166.4

    : 1531.7 : 5236.1


    110.8 51.1 50.5 3-3 5.8 21.9 1.6 7-4 4 8.8

    : 48.9 : 181.8

    ======================= Percentage : consumed : by


    3-5 : 2.8 4-9 5.6 1.8 4-8

    : 4-5 3-8 6.4

    : 5-3

    : 3.2

    : 3-5

    i s s s s s a s s a s i a Energy consumption, :

    mtoe * :

    Per capita:

    4.4 8.0 2.8 3-7 2.4 0.3

    : 0.1 0.7

    ! 0.6 : 0.1

    : 1.3

    : 1.4

    Per farmer : or farm : worker : 2.6 : 13.3 : 2.0 : 5.9 : 0.5 : 0.05 :

    : 0.02 i 0.21 : : 0.11 : : 0.03 :

    : 0.2 :

    : 0.24 : : 3 3 { 3 3 { 3 S S 3 S B B a BSS3B3ES2SS

    * mtoe " million tonnes of oil equivalent

    Source: P.A.O., The state of food and agriculture, 1976, Rome 1977


    8. The rise in energy prices has had less effect on agriculture than on other sectors. To begin with it mainly affected certain highly intensive crops (e.g. hothouse horticulture) or crops produced far from centres of consumption (transport costs). Since prices rose again in 1979/80, however, the energy crisis has had increasing repercussions on the economics of farms all over Europe. The cost of the energy (fuel, electricity, etc.), fertilizer and equipment necessary for agricultural production has risen much faster than the prices paid to the farmers for

  • 9 -

    their produce.This divergence between prices paid to producers and the cost of the means of production is illustrated in Figure 3. All prices have been deflated by the general index of purchase prices of means of production, which thus remains constant (= 100). The opening of the "price scissors" as shown in the diagram is the clearest illustration of how the energy crisis is affecting agriculture. Up to 1972, the movement of price differentials was generally in the farmer's favour. Since the 1973/74 oil crisis, however, agricultural prices have ceased to increase in proportion to energy input prices (direct and indirect), and the improvement in the situation in 1975 and 1976 was limited and temporary.

    9 European agriculture is therefore increasingly sensitive, in economic terms, to the worsening energy crisis and this sensitivity is liable to become more pronounced, even though energy costs (for direct consumption) represent a small percentage of the total costs of agricultural production (less than 6% on average). Not only have energy costs increased markedly (they have almost trebled since 1973); the prices of almost all other factors of production purchased by the farmer have also been affected, indirectly to varying degrees, by the rise in energy prices. This is the case for fertilizer, pesticides, seed, animal feed and equipment, all of which need energy for their manufacture and distribution. Their prices will reflect a rise in energy prices to a varying extent and with a time-lag depending on the amount of commercial energy incorporated in them, whether it has been possible to economize further on the energy used for their production (conditions of production) and the extent to which producers can pass on their increased costs (market conditions). In the case of equipment, which is replaced over a long period, the rise in prices will only gradually work through to the farming sector as replacements are purchased.

    10. The consequences of rising energy prices vary widely according to types and methods of production, the structure of production units, regions and countries. On the one hand the amount of energy consumed by agricultural production depends on the type of production and the extent to which energy is rationally used. On the other, direct and indirect energy costs

  • - 1 0 -

    Figure 3: Changes in costs of energy, fertilizer, inverstment in machinery and in prices paid to producers for agricultural products, in relation to the general index of purchase prices of the means of agricultural production (= 100) _

    I50 i


    L 1973 74 75 76 77 78 79 80

    Energy and lubricants , _ . _ . . Fertilizer and soil improver

    Inverstment in machinery Prices paid to producers for agricultural products

    Source: EUROSTAT

  • _ 11 _

    vary between countries and in many of them some sort of tax or duty concession is made to farmers. As examples: at the end of 1978, the price of tax-reduced diesel oil in Belgium was less than two-thirds of the price of tax-reduced diesel oil in the Netherlands, but the price of natural gas (for heating greenhouses) was three times as high in Belgium. Between 1973 and 1980 the price of fertilizer rose 21% more than agricultural prices in Germany, and 56 in Prance. The rise in energy prices may thus affect the competitiveness of regions and aggravate income disparities in European farming.


    11. If the agricultural sector is to adjust to the energy situation it must first, like other sectors, endeavour to save energy: some experts estimate that agriculture's present energy consumption could be reduced by 15-20 by appropriate action. This would include: - "tailored" application of fertilizers and pesticides; - choosing the most suitable machinery and using it efficiently; - using insulation wherever possible; - recovering the heat which is a by-product of certain forms of

    agricultural production (in particular dairy and stock farming); - finding substitutes for at least some indirectly consumed energy

    products (e.g., the use of waste, processed if necessary, as biological fertilizer to replace chemical fertilizer).

    12. But energy-saving is not the only adjustment strategy available to agriculture to combat the energy crisis. This sector is particularly well placed for using certain renewable energy sources which could in future partially replace non-renewable fossil fuels. Agriculture would then become an energy producer.

    In an initial phase it would be possible to consider using farm waste to produce energy in the form of heat (by combustion) or gas (by fermentation or gasification) which could then be used on the farm or in the village (no transport).

  • -12

    In a second phase, which would take matters much further, agriculture could make a positive net contribution to satisfying society's energy needs by producing energy biomass on a varying - but large - scale. This would require the intensive use of forests and underbrush and also the development and use of so-called energy crops (e.g., giant reed; short-rotation coppicing; euphorbia).

    15 As things stand at present, biomass as a renewable energy source seems very promising. A great deal of research is now in hand to investigate its possibilities and limitations in detail.

    It is certainly much too early for definite conclusions. The following chapters will deal briefly with the technical possibilities and the potential of biomass as an energy source, and with the socio-economic problems and political decision-making that such a strategy would entail, in particular for the European Community.

  • - 13 -

    Chapter 2



    14 Definition - Biomass is all the organic, animal and vegetable matter, plus by-products, deriving from photosynthesis, the process by which plants take up carbon by means of the chlorophyll in their leaves.

    15 General characteristics : Biomass is renewable but dispersed. The development of vegetable biomass is a function of temperature, light, water and nutrients. On the basis of these conditions certain regions of the world are better for biomass production than others. The "mass" is the dry matter produced per hectare per year, which may then be assessed in terms of tonnes of oil equivalent at the following rate :

    2 500 kg of dry matter 1 toe. This is a general equation which may be modified in certain cases (oil or wet substances, where account must be taken of the latent heat of evaporation).

    16. Basic materials which constitute 'energy biomass' Agricultural wastes and residues Certain agricultural by-products form the first category of materials which are immediately available; these are : a) plant wastes : straw from cereals and oleaginous crops, maize stalks

    and shucks, vine shoots, beet leaves and tops, and from wine-making, marcs etc;

    b) by-products from livestock : manure and slurry from sheep, cattle and pig pens, poultry droppings, whey and abattoir wastes.

    ]7 Forestry wastes and residues a) existing brushwood, much of which is used little or not at all

    (particularly in France and Italy); b) the products of thinning, which are not currently used commercially; c) wastes from forestry and wood-processing operations (saw mills;

    structural timber; board manufacture).

  • - H -18. Energy-producing crops

    In addition to the recovery of these by-products, there are plans to grow crops which are intended not for feeding men or animals, nor for other sectors such as textiles, but for producing energy. Such crops must meet certain criteria with regard to feasibility and profitability : they must yield a substantial amount of dry matter per hectare, have low production costs, be easy to harvest - and their energy budget must be in substantial surplus.

    The feasibility of growing certain crops for energy is being investigated in temperate zones; These are mainly brushwood with a short growth cycle likely to produce between 12 and 15 tonnes of dry matter per hectare per year. A plantation was established in Ireland in 1980 on former peat bogs. One or two particular plants might be attractive : bracken, gorse and broom, which are able to grow on poor soil and under adverse climatic conditions. Other plants which usually grow in tropical countries might be of some interest to European countries. The water hyacinth produces up to 150 t of dry matter/ha/year in a lagoon. Its ability to absorb pollutants (including metals) would give it a secondary role as an antipollutant in hot waste-water pools. Euphorbia (Euphorbia lathyrus and Euphorbia characias) grows on poor, dry soil and produces sap which is rich in latex with a composition similar to that of hydrocarbons. Certain plants are already being harvested for energy purposes : an experiment is under way in the South of Prance with the great reed, which yields an average of 15 tonnes dry matter/ha/year (l).

    19* Other plants have several possible uses, for food, industry and energy : a) Plants which yield, either after hydrolysis or directly, a sugary juice

    which can be fermented and turned into alcohol (which may be blended with petrol - up to 2% admixture being possible even at present) : sugar beet, fodder beet, sweet sorghum, Jerusalem artichokes, maize, potatoes and fodder kale;

    b) Oleaginous plants (colza, rape, sunflower, soya, flax etc.) might be considered since their products can fuel diesel engines.

  • - 15 -

    c) Catch crops : after an early harvest a new crop is sown for harvesting before the winter;

    d) Biomass produced from seaweed and marine algae is being studied. Productivity is potentially very high : 80 tonnes of dry matter/ha/year.

    20. Other products a) Organic waste from the agricultural and food industries : waste water

    etc. ; b) Urban wastes (domestic refuse; effluent); one advantage is that they

    are already collected.


    21. There are currently two types of biomass conversion : biochemical routes and thermochemical routes.

    I. Biochemical routes or biological conversion of biomass

    Biochemical methods can be used to process wet biomass, so avoiding the necessity for drying (which would be expensive). The main products are : alcohol, methane and direct production of heat.

    22. a) Ethanol production Various input materials may be used : potatoes, manioc, sugar beet, sugar cane, wood, wheat, maize and whey. The first stage of the process is to convert the cellulose, starch or sugars present in certain plants into sugary liquor.

    This can be done by means of acid hydrolysis or biological hydrolysis or by aqueous extraction. The second stage is based on alcoholic fermentation of the sugary liquor, which produces the ethanol for distillation. Ethanol for use as an energy source must have an alcohol content of at least 95* if it is to be blended with petrol, and this presupposes several stages of distillation. But distillation, by present methods, requires a great deal of energy and one also counts the energy inputs for growing, storing and transporting the raw materials, the energy budget for this route is not attractive.

  • - 16 -











  • - 17 -

    There are, however, advantages to using ethanol as a liquid fuel : - being liquid, it is easy to store; - a mixture of 10-15$ with petrol requires only retuning of the engine; - it increases the octane number and could be used in oil refineries for this purpose and thus reduce the amount of energy required to produce the petrol itself;

    - the by-products may be converted in their turn and used as animal feedingstuffs;

    - it is non-polluting during combustion. However, this rosy picture does have its thorny side : - for a mixture of more than 20$ considerable engine modifications are required;

    - the effluent from distillation is a pollutant; - research is still required to develop certain techniques, such as the enzymatic hydrolysis of cellulose;

    - production costs are currently far greater (by a factor of between 1.5 and 2.5) than the cost of importing oil;

    - the production of alcohol for use as an energy source is in competition with that of alcohol for human consumption.

    However, it is interesting to note that synthetic ethanol produced by the petrochemical industry (from naphtha) has an energy budget which is even less favourable than beet ethanol and from the point of view of energy efficiency, seen in isolation, synthetic ethanol should cease to be used as a chemical feedstock. It is essential to improve the entire ethanol production process to make the operation profitable from the cost point of view and to make a rational decision possible.

    23. b) Anaerobic digestion This is the conversion route for the production of methane. Using organic matter (animal excreta and industrial, agricultural, food and domestic waste) in an anaerobic environment and in the presence of water, the first stage is solubilization and hydrolysis followed by the formation of fatty acids by acid-forming bacteria. The action of methane-forming bacteria in the presence of heat generates methane. A gas is formed consisting of methane (60 to 70$) and carbon dioxide (30 to 40$), traces of hydrogen, and hydrogen sulphide. The calorific value of the methane is 9 500 kcal/Nm5.

  • - 18

    The main advantage of methanogenesis is that it permits a vide variety of waste to be used and promotes its recycling whilst acting as a purifier (slurry, waste water from the agri-food industry, etc.) since it reduces the chemical oxygen demand by approximately 50% and does not appear to reduce the fertilising capacity of the final effluent. The methane output may be used to produce heat with a burner, power with gas engines or electricity via an alternator, driven by a gas engine. The process may be continuous (a given proportion of the substrate is regularly topped up) or a batch process (all the material is introduced at once and emptied when digestion is completed; several digesters will be required if gas is to be produced on a regular basis). The difficulties with anaerobic digestion stem from the considerable investment required (new digesters to be designed and manufactured), the unimpressive energy budgets, because the digesters need to be heated, and the complex nature of the reactions involved in methanogenesis (further research needed).

    24 Investment for the manufacture of digesters There are two approaches to this type of problem :

    a) manufacturers' proposals for the design and manufacture of large automated digesters which are easy to use and need little handling. These digesters will be expensive and therefore only economic for large stock farms (80 livestock units or 1 000 pigs) because they keep down transport costs. They serve two purposes - purification and energy production;

    b) a "craft" or "do-it-yourself" approach, with small digesters made by the farmers themselves in their spare time and suitable for medium-sized stock farms (30 livestock units) to provide extra energy to run the holding.

    The point is an important one, since the latter kind of digester may be constructed for small, decentralised farms, whereas the former type is intended for large farms or centralised collection units. Both approaches are interesting and useful and the price might well be lower for digesters built in series.


    1 Caule shed 2 Excretor collection pit 3 Charge pump 4 Heated digestor 5 Gas-holder

    6 Electricity and heat generator 7 Domestic use of hot water and electricity 8 Use of hot water and electricity for a fodder drying installation 9 Storage of sludge and digested slurry

  • - 20 -

    25 The reactions involved in methanogenesis. Methanogenesis is a delicate reaction since it depends on achieving equilibrium between several bacteria. This equilibrium may be upset by over-acidity of the substrate (caused by the action of the acidogenic bacteria), by a drop in temperature (if the digester is filled too quickly or heating ceases), by a noticeable modification of the components of the substrate (animals treated with antibiotics; high copper content in pig feedingstuffs) or by the use of monensin (humensin) (a substance which prevents the formation of methanogenic bacteria during digestion in cattle). Given present knowledge and the technical performance of anaerobic digestion, it would appear that this conversion route must remain combined with purification functions if it is to be economically viable and also that there is a great deal of research still to be done to achieve lower break-even levels, particularly by dispensing with re-heating.

    26. c) Aerobic decomposition Many farms have used and some still do, the heat given off by decomposition of the organic matter in their manure heaps, as with all compost. It may be produced equally well from manure heaps or sludge stored in an aerated tank before spreading or from brushwood crushed to make compost. It is possible to recover the heat by placing a water circulation coil in the substrate, although it should be borne in mind that the temperature will not exceed 50 to 60*C. Only a small amount of energy is produced and a considerable amount of waste must be collected. In addition to heat production, this method has the advantage of producing an organic improvement for good quality soils, or of preventing forest fires after undergrowth clearance - which is a considerable point in its favour, particularly in Mediterranean countries.

    II. Thermo-chemical routes

    27* Unlike biochemical conversion routes, thermochemical processes require dry material and are carried out at high temperatures. The substances produced by thermochemical methods differ according to the processes used, a) Combustion Combustion, the complete oxidation of a substance, has been used for centuries and remains an important source of energy, world-wide/after oil,

  • - 21 -

    coal, wood and other heating materials. Combustion is generally effected in a boiler to produce heat for industrial processes and in a stove for domestic heating purposes. Problems with using different types of biomass (wood, straw, etc.) arise from storage of the fuel and feeding it to the boilers. Studies are being carried out in several countries (Denmark, the Federal Republic of Germany and France) to make the process more convenient through automatic charging and multi-fuel operation) to reduce the volume of the fuel - i.e. to convert it, say into the readily stored form of pellets or slabs, and to develop boilers which will take these new materials. Other difficulties to be resolved are the release of smoke and fumes, and tar deposits.

    28. b) Pyrolysie Pyrolysis is the decomposition of organic matter by heat (200 to 400*C) in the absence of air. It has been known for .a very long time from charcoal-burning and produces charcoal, a pyroligneous liquor (water, organic acids, resins, alcohol, etc.) and lean gas (l 000 to 2000 cal/Nm3). Charcoal has uses in chemistry, electrometallurgy and the iron and steel industry; the pyroligneous liquor is a raw material for the manufacture of resins (acetic acid, furfurol, etc.) and can be converted into fuel-oil (a mixture of charcoal and pyroligneous liquor). The gas can be burned to dry the wet organic material prior to pyrolysis. Research is being carried out to achieve total gasification (by flash pyrolysis for example ) which would improve the gas output and calorific value and avoid the production of tars. The liquor could be processed into plastics by polymerization, or into petrol or alcohol by hydration. In Europe pyrolysis is of interest principally to the chemicals and fine chemicals sector (the constituents of the pyroligneous liquors). Only a fairly small amount of energy is produced by combustion or gasification (see next section), which detracts from the usefulness of pyrolysis. Moreover, production costs are currently very high.

    29* c) Gasification The gasification of raw organic matter or charcoal is carried out in a gaeifier where it is subjected to temperatures of the order of

    * Flash pyrolysis is carried out at a very high temperature (lOOO'C) and in a very short time

  • - 22 -

    ETUDES DU CNEEMA - Feb. 1980 -No. 460


    . . . . . . . . . .

    < . > ; , . . ; '

    Vapour , Wood

    / Reaction zone

    ~^ Gas outled grid

    Ash box

    GOHIN-POULENC portable gas producer

    rrCE en

    lit 15 I. "V




    r m

    Additional air intake

    H \ Gas produced

    DELACOTTE gas producer

    I I Gas outlet

    Reheating pockets

    CNEEMA-PILLARD suspension ' ' gas producer


    Hearth \ ' Principal f~~ L air inlet

    Inverted flow gas producer - ^ .

  • - 25

    800 to lOOO'C in the presence of a controlled amount of air or oxygen. Charcoal can be gasified in this way. Gasification produces a gaseous mixture ("producer gas") which can be used to fire a furnace to provide heat or to fuel an internal combustion engine to provide power. Finally it is possible to obtain from this gas, which contains carbon monoxide and hydrogen, a synthetic methanol which may be used as liquid fuel. The energy yield of gasification is usually between 70 and 80^; 1 kWh of processed matter is obtained per 900 g. There is a great variety of gas producers on the market which have already been proven industrially. The main advantage of using gas producers for biomass is that it is possible to decentralize the procedure to a large extent with small units. This technique would also appear to lend itself to application in isolated rural communities in developing countries. Moreover, gas producers (fitted to lorries) might solve the problem of lack of liquid fuel. But there are difficulties with gasification; for example, the process is often incomplete and the unconsumed mass arrests it; there is some risk of pollution due to fumes, carbon particles and tars. Gas producers take only fairly large pieces of material, which rules out waste such as sawdust*. To run profitably, a gas producer should not be too big and should be operated continuously. Existing gas producers need to be improved, and various research teams are working to achieve this; it is worth pointing out that they were widely used during the last World War.

    30. d) Methanol production Methanol is an alcohol produced from gas. In France it is synthesised from natural gas but coal, oil and methane from biomass degradation or any biomass gasification are other possible sources.

    Methanol arouses interest because - like ethanol - it can be used as a (liquid) motor fuel and obtained from any biomass and not only by alcoholic fermentation, which requires fermentable glucides. It can even be turned into petrol. The process itself would seem relatively inexpensive if it

    * with the exception of the suspension gas producer.

  • - 24 -

    were not for the raw material - methanol is very expensive. Despite the problem of cost, research is being carried out on the process in the United States and New Zealand

    The factors which favour the production of methanol are as follows : - production from natural gas requires 0.88 toe per tonne of methanol yield. Current research is directed towards the gasification of wood with oxygen and appears to be well advanced. However, the production of methanol by gasification of wood requires only 0.23 toe per tonne of methanol (not counting the wood) whch is an immediate saving of 0.6 toe

    2 per tonne of methanol produced;

    - production sources are very varied : wood, algae or any lean gas; - engine efficiency is increased because of the higher octane number of methanol;

    - like ethanol, methanol obviates lead pollution; - although it is corrosive, methanol could be used straightaway in a blend

    (not more than 1.5% methanol). The main technical difficulties for using methanol as liquid fuel arise because it is still necessary to : - design an industrial gas producer which will supply a gaseous mix suitable for methanol synthesis. Research projects in hand appear to be very close to success;

    - modify engine intake systems to give a lower fuel/air ratio; - increase the compression ratio to take account of the higher octane number of methanol;

    - reduce its toxicity; - increase the size of the fuel tanks; - solve cold-starting problems; - modify the alloys used for engine components to reduce the corrosive effect of methanol;

    - set up an industrial infrastructure; in order to produce methanol/ high-capacity centralised units must be set up.

    * 1 tonne of methanol - 0.6 toe. 2 Speech by the Minister for Agriculture (France), October 1980.




    o 2 -->

    producer Gas

    J U U U O O ! Charcoal / ^

    Q Pump


    Cooling ! system

    & =


    Catalytic leonversion '

    Compression to 10 - 20 BARS

    D | Pump

    Source: EEC-DG XII - Prospectus Energy from Biomass 1980

  • - 26

    31. e) Hydoliquefaction or hydrocracking of cellulose Biomass can be converted into liquid hydrocarbons at high temperature and pressure in the presence of hydrogen or in a gaseous mix. Fuel oil is produced. The starting materials are wood and lignin, but this conversion route is only at the experimental stage and much research still needs to be carried out.

    Rapid results of hydroliquefaction of wood

    B S S 3 S X S S M







    B = a a m a : a = = = = s


    3% methanol 15% propanol 40% pulp

    8% methanol 13% alcohol 23% hydrocarbons

    32. In addition to the biochemical and thermochemical conversion routes, there is a route for oleaginous fruits which may be described as mechanochemical and consists in extracting the vegetable oils by pressing or by solvents, for later use in diesel engines. There are various plants from which oil may be extracted : ground-nuts, soya, colza, sunflower, olives, flax, mustard, jojoba, guayule, eucalyptus, etc. The oil can fuel diesel engines. The production method is well understood since it is currently used to obtain the edible oils. In general two processes are used : - extraction by pressing (by means of screw or hydraulic presses) usually used for olive oil;

    - solvent extraction : a volatile inert liquid, which is a strong solvent of fats, is passed through the raw material, or an initial mix obtained by pressing, at temperatures below 100'C. The oil dissolved is separated off by distillation from the solvent, which is recycled.

    There are various forms of equipment and numerous solvents on the market; they yield a maximum amount of high-grade oil. The residue from extraction is oil cake, which is rich in proteins and is being used in increasing quantities in Europe as animal fodder.

    STERN, A.J.; HARIS, E.E. 1953 - the chemical processing of wood - New York; Chemical Publishing Company.

  • - 27 -

    It is worth pointing out that one hectare of colza produces approximately 2 tonnes of oil cake, 0.9 tonnes of oil (- 0.9 toe) and 3 tonnes of straw.

    Many studies and experiments have been undertaken very recently on this crop : in Brazil, where the bus fleet should be using a mixture containing 16$ of vegetable oil by 1985; in South Africa, where numerous tests are being carried out to determine tractor performance; in the United States, where tests are being carried out on the performance of various mixtures; and in Austria, where certain studies indicate that engines are well-suited for running on vegetable oils (BPVA in Wieselburg).

    The most obvious advantages of this conversion route are as follows : - the method for growing the crops is generally well known to the farmers

    (particularly for colza and sunflower) and would not require any special training ;

    - the plant varieties grow in a variety of climatic conditions in the north and south of Europe;

    - certain oleaginous crops (soya and ground-nuts) promote nitrogen fixing and reduce the need for nitrogenous fertilizers;

    - the by-products (oil cake) are an important complement to animal feedingstuffs (of which 85% is currently imported);

    - finally, the extraction techniques are simple and established and the oil may be used in diesel engines without any significant modification; the oil is immediately usable as fuel and there is no need to create an extensive industrial infrastructure.

    There are nevertheless some problems still to be solved :

    - only engines with in-line injection pumps can cope with high vegetable oil contents;

    - vegetable oils are more viscous than fuel oils and need to be "fluidized" (by mixing or heating);

    - vegetable oil tends to form gums, to resinify and to produce carbon residues;

    - as with the production of alcohol and most energy crops, the arable land required for cultivation of the crops proposed will have to be made available.

  • - 28 -

    34 The various conversion routes cited above are largely processes already in use - some of them have been in use for a considerable time - but some are only at the laboratory stage Some of the equipments need to be developed and others improved. In addition, all the necessary equipment needs to be developed for harvesting, transporting and storing biomass, apart from that for oleaginous crops. Production of liquid fuel (methanol, fuel oil) appears to be one way to meet part of our energy requirements, particularly for automotive applications. Solution of the technical difficuties will partly determine the future of this avenue of development.

  • Anaerobic digestion


    Agricultural resources

    | Sun

    J Photosynthes .

    Forestry 1 resources

    | Water

    ^ ' ' Aquatic 1 organisms

    Biochemical conversion

    ! Aerobic , digestion

    Alcoholic fermentation



    i, Nechanochemical conversion

    Thermochemical conversion


    Extraction Pressing j \ [Solvent . Combustion

    I Gasification I Pyrolisis Hydro-; cracking

    Charcoal ' ' I J~Pyroli-I geneous I I liquor


    Lean gas Fuel

    Catalytic synthesis


  • - 30 -

    Chapter 3


    35 In the firat chapter energy analysis, or at least the tools of energy analysis - energy budget (balance) and yield - were used largely to illustrate the position of agriculture in relation to energy. It is no simple matter to apply energy analysis to a sector of activity and there is some confusion with regard to definition of the concepts used and their suitability for the calculations made. We shall therefore try in this chapter to clarify some of the definitions and the principal difficulties of energy analysis and then demonstrate its usefulness for calculating the potential of biomass.

    A. GENERAL DEFINITIONS I. Definition of energy analysis

    36. "Energy analysis is an attempt to evaluate the quantities of energy required, either directly or indirectly, to produce an article or a service" - G. Leach. Energy analysis is based on the assumption that it is possible to convert all the various forms of energy involved in production systems to one homogeneous unit. Energy forms are measured on a common scale either in joules or kilocalories.

    II. Definition of the tools for energy analysis.

    37 The energy budget is the calculated output (converted into energy units) less energy input (converted into energy units). This method makes it easier to evaluate quantities used and quantities produced (see Table l). Energy yield corresponds to the ratio between output and input (converted into energy units) for a given system. It shows the efficiency of a production system in relation to the energy flows (see Table 1). Yield Qnergy equivalent of production - output

    energy expended on production input

  • 31

    Studies based on energy budgets or energy yield may refer to an entire production sector (energy budget for French agriculture in a particular "department" or region), to a specific crop (maize), to a holding or given type of holding or again to biomass conversion routes (anaerobic digestion).

    Table 4 : Energy budget for some crops (toe/hectare) INRA Toulouse experiment

    : Wheat : Maize : Soya : Lucerne : ByeGrass i s i 8 i a i B 3 t i x s 8 i s a > S 3 i i B i s s a a a s : BIOMASS BALANCE YIELD

    Energy Produced Energy Consumed Difference PC Efficiency*

    : 4.5 : 0.59 : 3-9 . : 7.6

    5.2 0.53

    4-7 9-8

    ! 2.7 : : 0.30 : : 2.4 : : 9.0 :

    RECOVERY: Energy recovered : Energy consumed

    BALANCE : Difference RC YIELD : Efficiency

    : 2.2 : 0.59 : 1.6 : 3-7

    2.6 0.53

    : 2 .1 4-9

    1.4 : 0.30 : 1.1 : 4.6 :

    4.2 0.52 3-7 8.0 S a S 3 B l

    3-8 0.52 : 3-3 7-3

    3-9 : 1.11

    2.8 3-5

    I S B S B B S B a

    : 3-5 1.11 2.4 3.1

    Efficiency Energy produced or recovered = Y i e l d Energy consumed

    W. Hutter, INRA, Toulouse at the CENECA symposium, February 1980 Agriculture and Energy.

    III. Formalization of definitions

    38. Any production process may be represented as the conversion of one set of components, ("inputs") into another set of components ("outputs").

    Inputs LN ?

    Production Outputs

    There are input items, and each I. represents the quality of input item i. There are output items, and each 0. represents the output quantity j. The input flow (Fl) and output flow (FO) may be calculated from these data by the formulae : Input flow : FI = K.I, + K2I2 + I

    1 1 2 2 Output flow : FO = C ^ + C2O2 + C 0 p K. and C. represent the energy conversion factors assigned to the input items and output items to determine their energy value.

  • 32

    Inputs which are consumed directly in agriculture are represented chiefly by the calorific value of fuels and the cosumption of energy such as electricity. Inputs which are consumed indirectly in agriculture are represented by the energy content of fertilizers, seeds, irrigation, the energy content of materials and human energy required by the work.

    Using FO and FI the energy budget can be represented as follows : FO FI;.

    Yield may be written : Y FO

    FE This representation of energy analysis may be applied to any production process. The problems arise from the difficulty of evaluating input and output and the energy conversion factors (which are difficult to assess because of variations with time and place and in the product itself).

    39 The processes taken into account in the continuation of this study are : agricultural production processes; the process for converting agricultural waste and energy crops into fuel These may be represented as follows :

    Agriculural Production

    a) In agricultural production solar energy input is not generally taken into account, which explains why the yield is often greater than 1 under most conditions at present. The input items I, to I are usually set off against the output edible produce. The above diagram shows a balance between input and output; this balance may vary and we might in fact require a small amount of input for a considerable amount of output or vice versa; and there are many possibilities in between.

  • 33

    Agricultural Production

    In *Sp Itx It


    Waste Conversion) SR Fuel Process Ss Byproduct

    b) For the use of waste (normally discarded) as an energy source, products 0. to 0 from an agricultural production process and the actual input for the conversion process It, to It will be regarded as energy input for the conversion process. The following will be regarded as output : fuels 0_ produced and byproducts 0g, if any, from the conversion process itself.

    "n Im It

    Production of Biomass

    JS Conversion Process

    _^ SR Fuel _)Ss Byproduct

    c)For energy crops input is regarded as the I, to I required for the production of biomass and input I required for the conversion process. Output is regarded as the fuels 0_ produced and the byproducts 0g, if any, from the conversion process itself. The product 0 becomes input to the conversion process and the nature of the product 0 (wood, algae, or whatever) will affect the yield from the process. The same is true for the previous process (the waste may be straw or vegetable tops or the like).

    Although this has been expressed in simple terms a whole range of difficulties arise with regard to the methodology and conventions used in energy analysis. These are discussed below.

  • - 34


    I. Calculation of input

    40. (a) The forma of energy taken into account Ecologista have calculated the ecological yield of certain ecoayatema with the object of quantifying all the relatione and exchangee between living beings and their environment. The calculationa show the importance of solar radiation and of photosynthetically active radiation in a land or water environment. But these energy flows are never taken into account in the energy analysis of agricultural production. Despite the obvious importance of solar energy in living processes and in agriculture, it is not taken into account for energy analysis since it is neither a scarce nor an expensive resource. The main factors taken into account are typea of energy which preaent problema of exploration, extraction and transportation. This currently relates to coal, oil producta (petrol, gas oil, fuel oil), natural gaa and electricity, which are called "direct energy".

    41 (b) Evaluation of human energy as an input to any production process Methode for the evaluation of the amount of work carried out by man in a given production proceas vary considerably. Symposia have been organized under the aegis of the IFIAS (international Federation of Inatitutes of Advanced Study) with a view to defining and elucidating the concepta of energy analysis. The advice given by IFIAS on this problem ia that human work should not be taken into account except non-industrialized or barely industrialized economies. This recommendation is in line with the approach of certain authors like G. Leach, D. Pimentel, A. Lepape, F. Bel and A. Mollard and is usually observed. Note : Measurement of human work is important for comparing an industrialized production system with a production system based on human work (cf. Table 1 in the first chapter).

    42. (c) Calculation of energy flows The gross energy content of a raw material is defined by its net calorific value (NCV).

    NCV - The quantity of heat recovered by complete combustion of a kilogramme of the raw material in question, disregarding the condensation of fumes, smoke, etc.

  • - 55 -

    In order to obtain a quantity of energy in usable form a series of energy input stages is required (exploration, extraction, transportation and processing). This is true of fossil energy sources and of recyclable energy sources.

    It has therefore been proposed that these input factors should be worked out so as to define fuel energy cost as the total NCV of the energies required to prepare the fuel. In spite of this convention it is not uncommon to find as the energy equivalent just the NCV, or something in between. In the context of agriculture it appears that direct energy is generally very well accounted for, but that in the case of indirect energy it is difficult to know what has been included (intermediate products such as : fertilizers, weedkillers, pesticides ? average depreciation of the equipment used ? energy required for manufacturing the equipment used and, if so, the average depreciation of equipment ? human energy and, if so, how it is calculated ? feedingstuffs ? irrigation ? seeds ? etc). Such lack of precision makes the calculations somewhat less than reliable.

    II. Calculation of output

    43 (a) As pointed out in the first chapter of this study, traditional agricultural energy budgets show the energy contained in agricultural products as production outputs and their energy content is calculated from their calorific value on combustion or from their possible methabolizable energy (the difference between these two types of calculation is approximately 10/Q. This accounting technique masks the other aspects of agricultural products : their nutritional qualities, richness of composition, on the fact that they result from highly sophisticated processing. It is therefore difficult to reduce them to mere level of basic energy-vectors. It is because the exercise is particularly academic, and in order to make it easier, that energy equivalents for agricultural products are tolerated. See Table 5 which gives a series of energy equivalents for various products. It will be noticed that the coefficients vary from one author to another, depending on the calculation methods used.

  • - 36

    Where biomasa is used as an energy source the problem does not arise, in that the waste or even a given energy crop is of interest only for energy purposes : nutritional and other qualities are normally discounted.

    44 (h) However, the greatest difficulty in calculating outputs arises from considering harvesting and processwastes as losses (see diagram 2 in the first chapter). Since agricultural waste represents a considerable proportion of the energy potential of biomass, this type of approach must be questioned. In view of the calculation methods used by most authors, new calculations were necessary to work out complete energy budgets for a given product.

    (c) The polluting effects of waste are rarely assessed, although if they are used, or converted into energy, their adverse impact on the environment should be reduced and this should be estimated.

    III. Common measuring standard

    45 By convention, and in order to make calculations, it is necessary to reduce the various products and forms of energy to a homogeneous measuring unit. Using such a unit, it is possible to place a value on things which differ considerably in qualitative terms. The basic unit generally used is the calorie (1) or the joule (2). Other units of measurement are also of interest : the tonne of oil equivalent (toe), since it is very apt in the present context for showing the savings to be made. The measuring standard adopted in that case would be the calorific value of a tonne of oil. The tonne of coal equivalent (tee) is also used. Moreover, since the French and anglo-american systems differ, there is some point in keeping a conversion table permanently available to see what the figures would be in the unit one knows best or generally uses. A conversion table is given below.

    (1) Calorie : the heat required to raise one gramme of water at atmospheric pressure from 14.5C to 15.5'C.

    (2) Joule : the work done by force of one newton moving through 1 metre; 1 calorie = 41855 joules.

  • 37

    Table : Equivalence of units - JR Mercier - Energie et agriculture La choix cologique - published by Debard, Paris, 1978

    Calorie (cal)

    Joule (J)

    Kilowatt hour (kWh)

    Tonne of coal equivalent (tee)

    Tonne of oil equivalent (toe)

    Brithis Thermal Unit (BTU)








    Equivalent e.g. 1 J







    values as cross references joule - 0.239








    calories tee





















    * The calories in food are kilocalories (= 1 000 calories); the negative kilocalorie (French 'frigorie') is also equivalent to 1 kilocalorie.

    ** Different equivalents for a tee may be found; here we have assumed 1 tee 2/3 toe. The prefixes to a unit denote a multiple or a fraction of the basic unit : micro - 10"6 - 1/1 000 000 kilo - 13 - 1 000 giga - 10$ - 1 000 000 000

    milli - 10-3 - 1/1 000 mega - 106 - 1 000 000 tera - 10 1 2 = 1 000 000 000 000

    IV. Energy equivalence coefficients

    46. In order to quantify energy inputs and outputs, it is first necessary to have a coefficient of calorific equivalence for goods or services as a working basis (this coefficient will correspond to the amount of energy required to produce one unit of a product). A series of comparisons of the value of the coefficients used by various authors revealed that they differ widely - sometimes by as much as a factor of 2. The differences are generally explained when the authors's methods are known. It is therefore important to have some idea of the analytical tools used by each author and to know their limits.

  • - 38

    Table 6 : Summary of the coefficients for estimating agricultural energy output

    unit : 105 kcal/kilo

    : Product

    : Maize : Barley : Wheat : Potatoes : Sugar : Pulses : Cow's milk : Beef and veal : Pigmeat : Sheepmeat : Poultrymeat : Eggs

    G. LEACH

    3.10 3-35 0.76 3.90 -

    0.65 2.4 3-94 3.1 1.4 1.6


    4 4 4 0.9 0.64 4 0.6 1.8 3-3 1.8 1.6 0.096 (1)

    US of

    Department Agriculture

    348 3-49 3.30 0.76 3-73


    2.7 32 4.72 5-53 2.5 3.1 1.2 1.3


    t t t t

    (l) per unit.

    Sources : G. LEACH, "Energy and Food production", p. 100. R. CARILLON : Etudes du CNEEMA N" 404 p. 16 for crop products and N* 408 p. 59 for animal products.

    USDA : Agr. Handbook, 1963, N* 8, Composition of foods. F. BEL - Y. Le PAPE - . MOLLARD - Analyse nergtique de la production agricole - INRA - Grenoble - 1978

    V. Validity of energy analysis in time

    47 As a general rule energy budgets are precisely dated, for a specified year or a short period, so that the effects of climate on production may be corrected (in the case of agriculture). These budgets therefore represent the results for a given moment in the development of methods or productivity levels for crops and stockbreeding.

  • - 39 -

    If we take as an example Table 2 in chapter I on the estimating (1972/73) and forecasting (1985/86) of commercial energy consumption for agricultural production in Western Europe, it is clear that the energy budgets for agriculture will differ sharply between 1972 and 1985 owing to the considerable increase in the amount of fossil fuels consumed. The same will apply to a cereal crop or a biomass conversion route. It is likely, of course, that agricultural production and the efficiency of conversion routes will improve in time as a result of technological progress, and energy analysis must take account of this for the purposes of calculation. Developments in the course of time will alter the energy equivalence coefficients, which at first sight appears complicated. One way out might be to use mathematical models. But before we propose sophisticated tools, we must first have reliable, representative statistics.

    48. We have tried in the foregoing to show the many possible factors and variables used or ignored by the proponents of energy analysis. Nevertheless, despite this range of variables, energy analysis for agriculture can be correctly carried out in accordance with the tools mentioned at the beginning of this chapter (the concept of budget and yield). The most troublesome factor is still how to estimate indirect energy and define its components. Any study on the subject would therefore need to define its framework for analysis and explain the relevance of each of the variables. For follow-up to our work it is essential to take account of waste and losses in production systems and, since wastes are likely to become a considerable source of energy in the future, we think it of paramount importance that they should be accounted for, be it on a crop, a regional or a production-system basis. This would give a far more detailed picture of the potential of wastes in countries like ours.

  • - 40 -


    49. As shown by the model set out in the first part of this chapter, the energy required to produce waste is regarded as nil. When the waste is collected a series of input items are defined depending on the conversion routes. For an energy crop on the other hand, input accounting begin with the provision of energy inputs for production. But once "output" is obtained, wastes and energy crops for conversion may be accounted for by identical methods. Taking the ratio :

    m NCV of the fuel produced NCV of the raw material used

    for these two types of energy matter, as often done, Y is the overall yield of the conversion process. The energy budget, or the yield from waste and energy crops, will, of course, be calculated as described above. The net yield for both types may be expressed as follows :

    50. Yield from waste : Output . NCV of the fuel produced Input NCV of the raw material used

    + direct energy for collection, transport and storage + direct energy for the conversion process + indirect energy (in equipment and buildings)

    Yield from energy crops : Output . NCV of the fuel produced Input NCV of the raw material used

    + direct energy for collection, transport and storage + direct energy required for the conversion process + indirect energy contained in materials + indirect energy required for cultivation methods.

  • - 41 -


    Cellulosic materials



    Starch products (high moisture



    Hydrolis is


    Starch products (low moisture







    ' 30


    5f7 15r20 IO7I2





    i Ethanol



    1 1

    G. Pellizzi - New and recyclable energy sources in agriculture - for the FAO, June 1980

  • 42

    51. Aspects of importance include comparison of the energy yield processes for different crops or types of waste according to their ability to produce greater or lesser quantities of fuel (sugar beet or maize; straw or waste wood ). The table on page 41 shows the process and yield flow schemes for ethanol production from raw materials. It may be seen that different products produce different amounts of fuel by the same conversion route. This might favour the selection of one energy crop rather than another, but it is only one factor in the selection process; account must also be taken of agricultural, soil, climatic, economic and social conditions which favour a product in a given region, and of crop yields per hectare. All yield calculations must also include the following information : - whether the yields are for crops in open fields; - whether they are experimental yields; and - whether the yields relate to full-scale production.

    52. As shown in the diagram (page 43) setting out the production and conversion routes for waste and for energy crops, conversion routes require a direct energy input for their operation (heat for the digester in the case of anaerobic digestion; fuel for heating the distillation column for the production of ethanol; etc.). The following table is a good illustration of how energy budgets differ with differences in the level of direct energy input. It may be seen that the overall energy budget can be improved by varying the direct energy source used.

    53 - A further factor which should not be forgotten is the indirect energy which goes into the equipment and buildings needed for conversion processes (digesters, gasproducers, etc.). This is generally either overlooked or not specified. Once the fuel has been made it can be used by being converted into power (for stationary or mobile applications, heat or electricity. Thus it will do work, though not without heat losses, since the thermodynamic efficiency of an engine or boiler is always less than 100 %.


    Food production

    Input ^ Agricultural ^-


    Industry e



    Conversion route A

    Conversion route


    Conversion route C

    Waste from conversion

    u^_.4 . Processing tor another sector

    = Direct energy input required for the process " r

  • 44

    Energy budgets for alcohol production

    Energy Input source _i _i

    Crop distillation toe ha year or process agricul industry

    ture Use

    Blending normal compression

    idem idem idem

    kg of petrol equivalent


    0.6 0.6 0.6

    Output 1 toe ha

    1 year


    1.7 2.0 2.0

    Production: 1 : toe ha : 1 s year :

    + 0.3 :

    1.3 : 0.6 : 1.0 :

    Sugar cane (Brazil) fuel oil

    2.t Sugar : cane : (Brazil) bagasse s

    3 4. 5.


    Beet Beet

    fuel oil straw


    0.4 1.0 1.0


    Beet solar (l of surface area) 1.0


    0.6(2) idem 0.6 Short rotation poplars poplars (5) poplars 0.2

    Blending normal compression 0.45



    + 0.4

    + 3.0

    (1) 1 hectolitre of ethanol 0.05 toe on an NCV basis. (2) A thermodynamic solar facility produces the amount of energy required to construct

    it in 4 years. It is assumed that it could operate for 10 years. (5) Production of methanol by total gasification of wood followed by catalytic

    synthesis; yield is 15 tonnes/ha/year of dry material. Ph. Cartier in "Futuribles" January 1980, p. 26.

    54 Finally, as with agricultural production, where in the main the edible substances were quantified and waste and losses ignored, the byproducts of certain conversion routes should be taken into account. These are : the final effluents from anaerobic digestion, which produce a compost; and molasses and vegetable waste from the alcohol route, which can be converted into animal feed. These are rarely taken into account although they may improve the energy budget for a particular route or detract from it (distillery effluent).

    At the end of the capter a number of energy budgets and yields which illustrate the subjects studied will be given as examples.

  • - 45 -

    55 In conclusion, it can be said that the resulta of energy analysis provide a measure of the efficiency of a production system which is completely independent of the influence of monetary flows or market situations. The results also make it possible to establish temporal and spatial comparisons between production systems (cf. Table 1, Chapter I) and to produce forecasts based on technological trends. Energy analysis is a new tool which needs to be refined. It could throw new light on certain factors which have not received much attention so far : distinction between premium energy sources, with a high calorific value, and energy with a low calorific value, for example. We have tried to set out here those aspects most representative of the complex nature of this tool and of the field in which we wish to apply it. It is important to remember that the results of energy analysis are not an end in themselves and that they must be complemented by economic and ecological analyses.

  • - 4 6 -


    Giant reed

    20 tonnes of giant reed (dry matter)

    Crop input 0.7 toe

    Replaces 8 tonnes of heavy fuel oil or domestic fuel oil

    Extra cost in use 0.8 toe

    _ Crude oil saved: 8.8 toe

    ""* Balance: 7.3 toe ha"1 year"1 -~


  • Yield, t/ha

    Dry matter, t

    Potential energy yield, toe/ha/year


    Straw I 4 .

    Short | rotation forestry



    J' Combustion L 3 ,^T1

    + X



    9000 mJ low energy gas

    (CO, H2) | 1 toe/ha

    0.9 toe/ha 'j

    Final energy yield

    ) Grain 5 5

    Beet 4 0



    ^ 1? Mt 210T ethanol 30000 m3 20001 j

    low energy , ethanol gas ' 1 toe/ha |

    (CO.H2) I 3.2 toe/ha \ 1 toe/ha

    approxi- ' mately

    40001 ethanol 2 toe/ha

    Cattle slurry Pig slurry

    1 tonne of organic matter

    200 m' i mthane >

    1 mVLU/day , 0.17 toe/ha ,

    500 mJ mthane

    1.5 mVLU/day 0.42 toe/ha

    Waste from the \ 1 food industry \


    300 m' mthane

    0.25 toe/ha

    Source: OCDE - Meeting of experts, Paris, 19-22 May 1980, on the agri-foodstuffs industry and the energy problem.

  • - 48 -



    I. Availability of waste

    56. Figures given for the energy potential of biomass are sometimes highly impressive. For even if the yield of photosynthesis is very low (between 0.4 and 0.8$ for most plants over one year), a considerable amount of solar energy is fixed by plants each year by this process. Worldwide it is nearly ten times the amount of fossil energy consumed now each year.

    However, biomass is often highly dispersed and, with present harvesting techniques, difficult to tap. In addition, the plant matter which is readily available is not only used to supply energy. Man uses it to satisfy a large number of essential needs such as food, shelter, clothing, furniture and many chemical and pharmaceutical products.

    57 In European Community countries, biomass is for the most part cultivated for non-energy purposes, in particular for foodstuffs and for forest and industrial products. To begin with, therefore, analyses of biomass availability must concentrate on the wastes or residues from the production of these.

    Table 8 gives a general idea of the amount of wastes theoretically available from the main sectors of agricultural and forestry output in the Member States, Spain and Portugal. Calculations were based on (a) FAO statistics for agricultural production in 1978 (except for forestry by-products, where Community and national statistics have been used) and (b) a number of assumptions derived from the results of other research) regarding the ratio of products to waste. Obviously the figures can only be approximations of what is theoretically available.

  • Table 7 - Main agricultural and forestry wastes and by-products in Community countries. Spain and Porgual