Levington (original) (raw)

LEVINGTON AGRICULTURE REPORT

**Energy balances in the growth of oilseed rape for biodiesel and of wheat for bioethanol.**by I.R Richards. B.A, B.Sc., M.Sc., Ph.D., F.R.Ag.S.
June 2000
for the British Association for Bio Fuels and Oils (BABFO)
Carried out by: Levington Agriculture Ltd. Levington Park lPSWlCH Suffolk IP10 0LU
Te1: 01473 271818 Fax: 01473 659025

[**Summary**](#I. SUMMARY)

1. [**Introduction**](#1. Introduction)
2. [**Boundaries**](#2. Boundaries)
3. [**Crop production and energy output**](#3. Crop production and energy output)
4. [**Energy costs**](#4. Energy costs)
5. [**Energy Balance**](#5. Energy Balance)
6. [**Emissions and apparent recovery of N fertilizer** ](#6. Emissions and apparent recovery of fertilizer N)
7. [**Bases of calculation**](#7. Bases of calculation)
8. [References](#8. References)
9. [Acknowledgements](#9: Acknowledgements)
10. HOME

SUMMARY

1. An analysis was carried out of the support energy employed and useful energy produced by oilseed rape and wheat crops grown and processed for biodiesel and bioethanol respectively. The analysis was based on current data, in particular taking into account the significant increases in crop yields and in the efficiency of fertilizer nitrogen (N) manufacture that have occurred over the past two decades.

2. A subsidiary quantification was carried out of the emissions associated with the growth of the crops. The data arising were not interpreted but are provided in this report for use in wider assessments of emissions

3. For each crop, two situations were covered: that where straw is left in the field and that where straw is removed and transported to a heat or electricity generating plant. In the latter, the energy value of the straw was taken into account

4. Where straw was left in the field, biodiesel production was strongly energy positive, giving a yield of 1 GJ biodiesel for every 0.561 GJ support energy employed (a yield/cost ratio of 1.78). For bioethanol, the yield was 1 GJ for every 0.90 GJ support energy employed (a yield/cost ratio of 1.11).

5. Where straw was burned as fuel and oil seed rapemeal used as a fertilizer, the balance was even better -yield/cost ratios were 3.71 and 2.51 for biodiesel and bioethanol respectively. In other words, for every unit of energy used to produce biodiesel, 3.71 units were made available. Utilisation of straw energy by burning is a practical proposition .and analyses reported here indicate that it would make a strong contribution to a net energy supply from crops.

6. The analyses indicated that growth of oilseed rape for biodiesel would be energy efficient even if no credit were given to the straw. Growth of wheat for bioethanol would be strongly energy efficient only if the energy value of straw could be utilised.

7. Conclusions from the analyses are believed to be robust and conservative as the trends for increasing crop yields and for increasing energy efficiency in fertilizer manufacture are expected to be maintained and the values of some by-products (glycerol in biodiesel production and bran in bioethanol production) have not been included. If evaluation of glycerol as a fuel is successful (this is underway in Austria), the energy balance for biodiesel would be significantly improved. Indeed, the energy yield/cost ratio for the biodiesel would be raised to 2.19 (excluding straw). Indications are that future trends for energy balances in both biodiesel and bioethanol systems will be positive with biodiesel in particular becoming increasingly attractive.

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1. Introduction

There are two main components to the total energy input to growing crops: that involved in farming operations and materials and that converted from radiant to chemical form by photosynthesis. The chemical energy content of harvested crops can exceed the energy input through farming operations and materials due to this contribution from photosynthesis. Crops can therefore act as net sources of useful energy through their utilisation of sunlight. The purpose of the analyses reported here was to determine if crops do indeed act as net energy sources in the particular situations where oil seed rape is grown for the production of biodiesel and where wheat is grown for the production of bioethanol.

Analyses take into account the energy costs for the manufacture and distribution of inputs to the crops as well as direct operations on the crops, and the energy content of the harvested crop and of the manufactured biodiesel or ethanol. -that is, life cycle analysis (LCA) approach (2, 27). Analyses of energy use in agriculture have been conducted, many in the 1973 - 1976 period of oil shortages, but results are now outdated, technology having changed (1,5,7,8,9,18,19,23,24,25,26,31). In particular, the energy cost for manufacturing N fertilizers has reduced from 65 -75 MJ/kg N in the 1970s to 30 MJ/kg N in the most modem plants. Crop yields also have increased by 30 - 40% over the same period. The analyses reported here are based on current data.

The introduction of set-aside as a component of EU agricultural policy has made available significant areas of land for which the only agricultural use is production of non-food and non-feed crops. Oilseed rape and wheat grown for biodiesel and bioethanol are acceptable for growing on set-aside land and so put to good use land which would otherwise be wasted. Both crops can be autumn ('winter') or spring sown but yields are higher, and the choice of varieties greater, with autumn sowing. Crops grown for biodiesel or bioethanol production would almost always be autumn sown.

Straw of both crops may be ploughed into the soil (or otherwise incorporated) or baled and removed. Where there is a heat or electricity generating plant in the locality (say within 50 km), straw represents a useful energy source. Recommendations for fertilizer p and K are adjusted to take into account the loss of these nutrients where straw is removed.

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2. Boundaries

The following items and processes are considered here:

The energy employed in farm machinery and buildings and in lorries used for transport is not considered as these items would be in-place already for other purposes. Processes downstream to manufacture of biodiesel' & bioethanol are not considered. Emissions involved in the manufacture of agrochemicals and packaging and in the provision of seeds (other than those involved in transport to the farm) are not considered. These would be small relative to the main sources in vehicle operations and fertilizer manufacture.

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3. Crop production and energy output

3.1 Yield and N input For oil seed rape and for wheat, the main input determining yield is fertilizer N. The relationship between the amount of N applied and crop yield is quantified in field experiments where yield is measured at different rates of N application. When yield is then plotted against rate of N application, a diminishing returns curve usually emerges and this can be described by a fitted regression function. This function can then be used to calculate the economically optimum rate of N application.

Data for this report were taken from two series of trials (15 trial each on winter wheat and winter oil seed rape) funded by Hydro Agri (UK) Ltd and conducted by Levington Agriculture Ltd. Trials were conducted on commercial crops in different parts of England representative of the main arable areas In 1994 to 1998. General growing conditions for the trials were typical of good farm practice. Trial design was replicated and involved several sources of N that Hydro Agri were evaluating. Results for the standard source, ammonium nitrate (the principal source of fertilizer N used on the crops In the UK and other European countries), are used here and are shown in[ Table 1](levington%5Ftables.htm#Table 1) for oil seed rape and in [ Table 3](levington%5Ftables.htm#Table 3) for winter wheat. Throughout this report, rapeseed yields are expressed on a 9% moisture basis and wheat grain on a 16% moisture basis.

Offtake of nitrogen in rape ([Table 2](levington%5Ftables.htm#Table 2)) and wheat grain ([Table 4](levington%5Ftables.htm#Table 4)) at different rates of applied nitrogen (kgN/ha)

Mean data from these trials are typical for the two crops in the UK and are shown in graphical form in[Figs 1&2](levington%5Ftables.htm#Fig 1) (oilseed) and [Figs 3&4](levington%5Ftables.htm#Fig 3) (wheat). Data points are described well by fitted quadratic regression functions:

• Yosr = 2.31 + 0.0165N -.0000369N2 (1)
• Yww = 5.03 + .0344N -.0000730N2 (2)
• where Yosr is yield of rapeseed t/ha
• Yww is yield of wheat grain t/ha
• N is rate of applied N kgN/ha

Economically optimum rates of N application are calculated for different assumed values for the cost of fertilizer N and price of seed or grain. The relationships between optimum N rates and prices of seed or grain are shown in[ Fig 5](levington%5Ftables.htm#Fig 5) (oilseed) [Fig 6](levington%5Ftables.htm#Fig 6) (wheat) for three assumed costs for fertilizer N. The costs of �0.3, �0.35 and �0.4/kgN are equivalent to (�1.03, �121 and � 138/tonne of ammonium nitrate. The lowest of these prices is current (May 2000) but there is some upward pressure due to a recent series of capacity reductions in Europe.

For oil seed rape, a seed value of �120/t corresponds to an optimum N rate of approximately 180kgN/ha. This optimum is little affected by price of fertilizer N within the assumed range and, from equation (1) above, corresponds to a yield of 4.08t/ha.

For wheat, a price of �75/t corresponds to an optimum N rate of approximately 195kgN/ha at the current fertilizer N price and, from equation (2) above, to a yield of 8.96t/ha.

For present purposes therefore, it is assumed that fertilizer N applications are 180kgN/ha to winter oilseed rape and 195kgN/ha to winter wheat and that the crop yields are 4.08t/ha and 8.96t/ha respectively. At these seed and grain yields, there will be associated production of straw at 4 t/ha and 6.5 t/ha respectively (expressed on a dry-matter basis). The assumed yields are often exceeded in practice, yields greater than 5 t/ha for oilseed rape and 11 t/ha for wheat being regularly reported. There is a long standing trend for yields to increase by 1 - 2% annually..

3.2 Energy value of crop yields One tonne of rapeseed contains typically 40 - 41% oil. Yield of oil following crushing and separation of cake is approximately 0.37 t with approximately 0.58 t of cake. On processing, the oil yields a similar amount of biodiesel with an energy value of 36 MJ/kg. lf rape is grown on set-aside land, the cake produced can not be used for livestock feed. However, it is useful as an organic fertilizer with a nutrient content of 6% N, 2.7% P

2O5 and 1.9% K2O (29). Of these nutrients, approximately 50% of the N is available to crops in the year of application and the P2O5 and K2O would be as effective as other sources where applications are for soil maintenance (the most common situation) (21). An energy credit can therefore be applied using data from section[ 4.2](#4.2 Fertilizers) below.

One tonne of wheat grain, on processing, yields approximately 276 kg ethanol with an energy value of 30 MJ/kg (13). There is a further 35 kg bran by-product which can be used as a fertilizer, once composted (project underway at Levington Agriculture funded by EU/HGCA). For present purposes, no energy credit is given for the bran, the quantity in any event being small.

For both oil seed rape and wheat, an energy credit equivalent to 15 MJ/kg straw is applied where the straw is removed from the field and utilised as an energy source. The energy value of oil seed rape and wheat crops is summarised in[Table 5](levington%5Ftables.htm#Table 5:) (Energy values of oilseed rape and wheat crops).

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4. Energy costs

4.1 Agricultural fuels
Fuel consumption figures are based on data provided by John Deere supplemented by Nix (24), and adjusted wherever necessary following review by agricultural contractors (28). It was assumed that minimum tillage techniques would be used for oil seed rape but that ploughing would be used for wheat. Wheat tends to be grown on heavier land and infestations of some weeds, notably blackgrass, are best controlled by ploughing.[ Table 6](levington%5Ftables.htm#Table 6) shows the values assumed for the different operations that may be employed in both conventional and minimum tillage systems.

Some of these operations occur more than once during growth of a crop. There would normally be two cultivations between ploughing and drilling of wheat. Fertilizer would normally be applied on three occasions to each crop, one application of P and K in autumn followed by two top-dressings of N in spring. Spray applications would normally comprise two herbicides in autumn, insecticide in autumn, insecticide + fungicide in spring and fungicide in autumn for rape (five applications in total) and herbicide in autumn and spring and two fungicides in spring for wheat (four applications in total). The operations actually carried out in a minimum tillage system for oilseed rape and in a conventional (ploughing) system for wheat are shown in[ Table 7](levington%5Ftables.htm#Table 7) together with related fuel consumption. It was assumed that the energy equivalent for diesel fuel is 43 MJ/l (26). The fuel energy expended in farming operations was then calculated and is shown in Table 7.

4.2 Fertilizers
The amounts of N applied are assumed to be 180 kgN/ha for oilseed rape and 195 kgN/ha for wheat (see section 3.1 above). ln addition to N, there would be one application to each crop of P and K, usually in the form of a compound fertilizer blended from triple superphosphate and muriate of potash (potassium chloride). The rates of application of these nutrients should be close to those recommended in MAFF Bulletin RB209 (20) for a typical soil index of 2 for each nutrient: 50 kg P2O5/ha and 40 kg K2O/ha for oil seed rape and 70 kg P2O5/ha and 90 kg K20/ha for wheat where straw is removed from the field. Where straw is ploughed in, recommendations for wheat are reduced to 60 kg P2O5/ha and 45 kg K2O/ha. These assumed rates of fertilizer application are similar to those reported in practice for Great Britain in 1998 (3): 204, 69 and 71 kg/ha for N, P2O5 and K2O on winter oilseed rape and 183, 68 and 77 kg/ha for N, P2O5 and K2O on wheat. Energy equivalents for fertilizer N (as ammonium nitrate), P2O5 (as superphosphate) and K2O (as muriate of potash) have been quantified by Laegrid et al (17) on the basis of current best available technology.

For solid ammonium nitrate, production in the most modem plants involves a total expenditure of 30.5 GJ/t of N. This is much lower than estimates made around 1975 due to improvements in ammonia fixation and other process technologies. Previous generation technology involved expenditure of 46.6 GJ/t N. For present purposes, a value of 38 GJ/tN is assumed. The mining of rock phosphate involves expenditure of 0.3GJ/t P

2O5 but, in the most modem plants, subsequent processing into triple superphosphate involves a net release of 3.8 GJ/t P2O5 of useful energy as heat. Older technology involved a net input of around 5 GJ/t P2O5 as triple superphosphate (Kongshaug pers. Comm.) from mining to granular product. For present purposes, a value of 3 GJ/t P2O5 is assumed. Mining, beneficiation and processing of muriate of potash involves expenditure of 2.5 GJ/t K2O in most modem plants, 5.9 GJ/t K2O in older technology. A value of 5 GJ/tK2O is assumed. Amounts of energy expended in fertilizers are shown in Table 8, converted from GJ to MJ.

[Table 8](levington%5Ftables.htm#Table 8): Energy equivalents for fertilizers used in crop production

4.3 Agrochemicals (herbicides, fungicides and insecticides)

Typical applications for oilseed rape would be one pre-emergence (metazaclor at 0.5 kg a.i./ha) and one post-emergence (tluazifop-p-butyl at 0.5kg a.i./ha) herbicide application, one flea-beetle spray (cypermethrin at 0.025kg a.i./ha) one fungicide application (flusilazole at 0.25kg a.i./ha) and one insecticide + fungicide application (iprodione + thiophanate-methyl) at 0.5kg a.i./ha). Total assumed application is 1.775kg a.i./ha, equivalent to 5.3 kg product (including packaging).

For wheat, typical applications comprise one autumn herbicide (isoproturon at 2.5kg a.i./ha), one spring herbicide (CMPP at 2kg a.i./ha) and two spring fungicide (stobilurin/triazole at 0.5kg a.i./ha each) applications. Total assumed application is 5.5kg a.i./ha, equivalent to 16.5 kg product (including packaging).

An energy equivalent for all agrochemicals of 190 MJ/kg a.i. was assumed (16). Assumptions made elsewhere include 250 MJ/kg a.i. (19) and 101 MJ/kg a.i. (25,26).

4.4 Seed

Typical seed rates of 7 and 185 kg/ha for oilseed rape and wheat respectively are assumed. An energy equivalent of 5 MJ/kg seed is assumed to take into account growth of the seed crop and processing of seed.

4.4 Packaging

It is assumed that fertilizer is delivered to the farm in 500 kg polyethylene/polypropylene IBC bags, agrochemicals in polyethylene containers and seed in paper sacks. Assumed amounts of packaging are 0.0022 kg (4), 0.0030 kg and 0.0050 kg per kg of fertilizer, agrochemical (a.i.) and seed respectively. Values for agrochemicals and seed were arrived at by weighing a sample of relevant containers and bags. Energy equivalents of 180 MJ/kg are assumed for plastic containers including IBC. (27) and 150 MJ/kg for paper sacks. Calculated energy equivalents for packaging are shown in[Table 9](levington%5Ftables.htm#Table 9) (Energy equivalents of packaging)

4.5 Transport

It is assumed that the farm is 60 miles (approximately 100 km) from the manufacturing or principal distribution centres for fertilizers, agrochemicals and seeds. It is also assumed that the farm is 60 miles from the processing plant to which seed or grain are delivered and, where straw is utilised, 30 miles from the site to which it is delivered. It is further assumed that these materials are delivered on 38 t gross weight (20 t payload) lorries which return empty. In practice, seeds and agrochemicals would be delivered on these lorries to a local merchants store and dispatched from there to the farm on smaller lorries or vans. To a lesser extent, fertilizers also may be delivered to the farm from a merchants store. The energy costs of local deliveries in smaller lorries are difficult to quantify because several deliveries may be made during the year. The amounts of fuel used are likely to be small relative to the uncertainties involved in the main distance assumptions above. However, 5% has been added to the assumed fuel consumption to allow for local deliveries.

It is assumed that rapeseed and grain for processing leave the farm in 38 t gross weight (20 t payload) lorries and that these lorries have no load on the journey from processing plant to the farm. The same size of lorry is assumed for transport of straw but with payload reduced to 15 t.

A fuel consumption of 0.58 / diesel/mile (0.35 / diesel/km) is assumed and an energy equivalent of 43 MJ/1 diesel. Energy costs for distribution are summarised in [Table 10](levington%5Ftables.htm#Table 10) (Energy costs for distribution to the farm and from farm to processing plant)

4.6 Processing rapeseed and grain into biodiesel and bioethanol

Energy costs for these processes have been quantified at 428 MJ/t biodiesel for rapeseed crushing (10) and 11.0 GJ/t biodiesel and 23.3 GJ/t bioethanol for processing (13). Both estimates are based on natural gas as the primary energy source for processing. For the crop yields and energy contents specified in section 3.2 above, these estimates are equivalent to 17251 MJ/ha and 57620 MJ/ha for oilseed rape and wheat respectively.

Production of biodiesel yields by-product glycerol at 0.04 t/t rapeseed. Other sources of glycerol are soap manufacture (where glycerol is a by-product) and synthesis from petroleum products. The use of glycerol as a fuel for co-firing in biomass plants or as fuel in diesel engines is being investigated in Austria so this by-product has material and probable thermal benefits. For present purposes, a potential energy credit of 35 MJ/kg, equivalent to 5712 MJ/ha at the assumed rapeseed yield of 4.08 t/ha, is given to glycerol. This value is not included in the main calculations but is included in section 5.2 below on the impact of glycerol use as a fuel. Production of bioethanol yields by-product stillage at 0.38 t/t grain (13) that is useful as an animal feed. Stillage has been given an energy value of 2 MJ/kg (13) so for the assumed wheat yield of 8.96 t/ha, there would be an energy credit of 6810 MJ/ha. The net energy cost for processing grain into bioethanol is therefore 50810 MJ/ha. The inclusion of an energy credit depends on the acceptability of stillage as an animal feed where the wheat feedstock is grown on set-aside.

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5. Energy Balance

5.1 Basic calculations

Energy balances for different situations are summarised in [Table 11](levington%5Ftables.htm#Table 11).

5.2 Impact on the energy balance if glycerol is used as a fuel

The energy balance for biodiesel is significantly improved if glycerol is used as a fuel. With a value of 5712 MJ/ha (see section 4.6above), glycerol use would reduce the total energy costs for biodiesel by the same amount and increase the energy balance from 25157 to 30869 MJ/ha where straw is ploughed in and from 84500 to 90212 MJ/ha where straw is utilised. The energy costs per GJ of biodiesel would be reduced from 561 to 456 MJ where straw is ploughed in and from 573 to 468 MJ where straw is utilised.

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1. Emissions and apparent recovery of fertilizer N

6.1 Emissions in fertilizer manufacture and agriculture

Sections 6.1 and 6.2 are intended to act as sources of relevant data to be used in conjunction with those from other sources in analyses outside the scope of this report. Emissions may be to atmosphere (mainly NH3, NOx and CO2) and to water (N and P compounds) and occur during fertilizer manufacture, from the soil after fertilizer application and during vehicle operation. There are emissions to atmosphere and to water from all soils, whether or not fertilizers are applied. Figures given here therefore refer to additional emissions that can be associated with fertilizer use.

Data for emissions from a modern fertilizer-manufacturing complex, established by EFMA (12) are summarised in [Table 12](levington%5Ftables.htm#Table 12) (Emissions from a modem fertilizer manufacturing plant. (Figures in parenthesis are mean values)).

Technology now being introduced will reduce N2O emissions from nitric acid plants by some 80%.

Taking the mean values from Table 12 and the assumed rates of fertilizer application, emissions can be quantified on the basis of land area for oilseed rape and wheat ([Table 13](levington%5Ftables.htm#Table 13)).

The main emissions following fertilizer application are NH3 and N2O to air and nitrate-N to water. NH3 emissions following fertilizer application have been summarised by ECOTOC (11). Under UK climatic conditions, around 0.02 kg NH3 is lost for every kg N applied as ammonium nitrate.

Published data on emission of N2O following fertilizer application have been summarised by Granli and Bockman (14). The range for emission is 0.4 -1.7 kgN2O for every 100 kg N applied as ammonium nitrate. A value of 1.0 kg N2O/100 kg N is assumed

N may be lost to water by leaching to an extent that will depend on soil and climatic conditions and by the efficiency of fertilizer use. Where N is applied after the main period of leaching (that is after mid-February in the UK), and at a rate not exceeding the economic optimum, the risk of leaching will be low (15,20). The proportion of N applied as ammonium nitrate that is lost by leaching is assumed to be 0.01.

CO2 and NOx are emitted during vehicle operation at typical rates of 2.6 kg CO2 and 40g NOx/l diesel respectively (12). These rates of emission are assumed for both farm tractors and lorries. For oilseed rape, total diesel consumption is 162 l/ha where straw is ploughed in and 210 l/ha where straw is utilised. Corresponding values for wheat are 167 l/ha and 222 l/ha. Total emissions of CO2 and of NOX are dominated by those arising from vehicle use. There would be therefore a significant beneficial effect on emissions, particularly of CO2, if biodiesel were used for transport and farming operations. In this case, CO2 released during vehicle use would be recently fixed and so would not represent a net addition to the atmosphere.

Emissions during fertilizer manufacture and following application are summarised in Table 13. The values shown should be regarded as typical and subject to considerable variation due to differences among fertilizer plants in level of technology and among crops in soil and climatic conditions. The efficiencies of both fertilizer manufacture and crop growth are also strongly influenced by management.

[Table 13](levington%5Ftables.htm#Table 13) Emissions during fertilizer manufacture, following application and during vehicle operation expressed on a unit area basis.

6.2. Apparent recovery of applied N in the crops The amounts of N removed from the field in rapeseed and grain are shown in [Table 2](levington%5Ftables.htm#Table 2) and[Table 4](levington%5Ftables.htm#Table 4) and in [Fig 1](levington%5Ftables.htm#Fig 1) and[Fig 2](levington%5Ftables.htm#Fig 2). Relationships between the amounts removed and those applied are curvilinear and are described by equations 3 and 4:

Nr = 54.69 + 0.467N -0.000804N2(3) Ng = 64.99 + '0.624N -0.00083JN2(4) where Nr is N offtake in rapeseed kgN/ha Ng is N offtake in wheat grain kgN/ha N is rate of applied N kgN/ha

The apparent recovery of N in rapeseed or grain at any rate of applied N can be calculated by differentiating equations 3 and 4. Apparent recovery is defined by:

Nar = (Ny -Ny0)/Nx (5) Where Nar is apparent N recovery at N rate Nx expressed as a proportion Ny is N offtake at N rate Nx kgN/ha Ny0 is N offtake where no N is applied kgN/ha

At the assumed rates of fertilizer N application ( 180 kgN/ha and 195 kgN/ha for oilseed rape and wheat respectively), apparent recoveries of applied N are 0.32 and 0.46 for oil seed rape and wheat respectively. Thus, for oilseed rape, an amount of N equivalent to 68% of that applied is not accounted for in the grain. The corresponding figure for wheat is 54%. This unaccounted for N occurs in the straw and as an accumulation in soil organic matter. Only a small proportion, equivalent to around 1% of that applied will be lost to air or water in the year of application.

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7. Bases of calculation

Figures in sections 1 to 6 above, calculated on a unit area basis, are summarised below and shown on different bases in[ Tables 14](levington%5Ftables.htm#Table 14) (Summary of energy values and costs) and in [ Table 15](levington%5Ftables.htm#Table 15) (Summary of emissions).

Table 14 shows that, if only the energy values of the biodiesel or bioethanol are taken into account (ignoring the value of straw and cake), all systems considered provide a positive energy balance -the ratio of energy cost to energy value of the biodiesel or bioethanol is less than 1. This is most marked for biodiesel where less than 0.6 GJ is employed in producing 1.0 GJ of biodiesel. TOP

8. References .

• 1. Anon. ( 1974) Report of the energy working party. Joint Consultative Organisation for Research and Development in Agriculture and Food, London.
• 2. Anon. (1990) Life cycle analysis for packaging environmental assessment. Proc. Specialised Workshop, Leuven, Belgium, September 24/25th, 1990.
• 3. Anon. (1997) Fertilizer use on farm crops for crop year 1996. The British Survey of Fertilizer Practice.
• 4. Bailey, M. R. (1992) LCA analysis of HFL packaging systems. Internal memo dated June 18th 1992, ref.1MM/MRB/JW/lcaanal.mem
• 5. Blaxter, K. L. ( 1975) The energetics of British agriculture. J. Sci. Fd Agric. 26 1055-1064
• 6. Bouwman, A. F. (1990) Exchange of greenhouse gases between terrestrial ecosystems and the atmosphere. pP 61-127 in A. F. Bouwman (ed) Soils and the greenhouse effect. John Wiley Et Sons Ltd, Chichester.
• 7. Crozier, J. F. ( 1976) Use of fertilizers considering especially nitrogen. ln Energy Use and British Agriculture, Reading University Agricultural Club.
• 8. Cunney, M. B. (1974) Energy use and farm machinery. Farm and Food Research 57-9.
• 9. Dwyer, M. J. and Mathews, J. (1976) Efficient use of farm machinery. ln Energy Use and British Agriculture, Reading University Agricultural Club.
• 10. ECOTEC Research Ltd (1999) Financial and Environmental Impact of Biodiesel as an Alternative to Fossil Diesel in the UK. Report prepared for BABFO.
• 11. ECETOC (1994) Ammonia emissions to air in Western Europe. Technical Report No.62.
• 12. EFMA (1997) EFMA Environmental Report for 1996. (AC-F1DUClA1RE 11/9/97) European Fertilizer Manufacturers Association, Brussels.
• 13. Gover, M. P., Collings, S. A., Hitchcock, G. S., Moon, D. P. and Wilkins, G. T. (1996) Alternative Road Transport Fuels -A Preliminary Life Cycle Study for the UK. Vol. 2. ETSU, London, HMSO.
• 14. Granli, T and Bockman, 0. C. ( 1994) Nitrous oxide from agriculture. Norwegian J. of Agric. Sci. Supplement No.12.
• 15. Jenkinson, D. S. (1986) Nitrogen in UK arable agriculture. J. Royal Agric. Soc. England 147 178-189.
• 16. Jones, R P. (1974) Energy considerations in crop protection. Outlook on Agriculture 8 141- 147.
• 17. Laegrid, M., Bockman, O. and Kaarstad, O. (1999) Agriculture, Fertilizers and the Environment CABI Publishing, Norsk Hydro ASA>
• 18. Leach, G. and Slesser, M. ( 1979) Energy equivalents of network inputs to food producing processes. Mimeograph, University of Strathclyde.
• 19. Lewis, R A. and Tatchell, J. A. (1979) Energy in UK agriculture. J. Sci. Fd Agric. 30449-457.
• 20. MAFF Solving the nitrate problem: progress in research and development.
• 21. MAFF Fertilizer Recommendations (RB 209) London, HMSO.
• 22. Nix, J.(1996) Farm Management Pocketbook. Wye College, University of London.
• 23. Osboum, R F. (1976) Forage conservation and support energy use. In Energy use and British Agriculture, Reading University Agricultural Club.
• 24. Pain, B. F. (1975) The energy to grow maize. New Scientist 15th May 1975.394-396.
• 25. Phipps, R. H. and Pain, B. F. The efficiency of energy use in forage maize production. In Bunting, E. S., Pain, B. F., Phipps, R. H., Wilkinson, J, M. and Gunn, R. E. (eds) Forage Maize Production and Utilisation ARC, London.
• 26. Pimental, R, Hurd, L. E., Belloti, A. C., Forster, M. J., Oka, 1. N., Sholes, 0. R and Whitman, R. J. (1973) Food production and the energy crisis. Science 181 433-449.
• 27. Richards, 1. R. ( 1991) Fertilizers: the present situation on LCA. Proc. llR Conference The Practical Application of Product Life Cycle Analysis, London, September 12th 1991.
• 28. Self, G. J. Pers. Comm.
• 29. Wallace, P. A., Boon, S. M., Bowen, P., Walker, K., Gray, M. and Bevan, K. (1999) Oilseed rape as a turf fertilizer. HGCA project report no.0536.
• 30. Webster, C. P. ( 1996) Factors controlling nitrous oxide production from arable land. Proc. SO Symposium, London, January 16th 1996.
• 31. White, D. J. (1975) Support energy use in forage conservation. Annual Conference, Institute of Agricultural Engineers, London.

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9: Acknowledgements

For the help given in the preparation of this document by

• John Deere Ltd
• Hydro Agri U.K. Ltd
• Fertilizer Manufacturers Association

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More information is available from BABFO at:
BABFO Office, Attention: Peter Clery, Curlew Court, Guy's Head, Sutton Bridge, Spalding, Lincolnshire PE12 9QQ U.K. phone:(044) 01406 350848 Fax: (044) 01406 351791 or email

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