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Evaluation of combined food and energy systems for more efficient land use and environmentally benign sustainable production

Contract nr: FAIR-CT96-1449
Project nr: 1449
Project type: SC
Starting date: 01/02/1997
Duration: 40 months
Total cost: 1,252,000 EUR
EC Contribution: 874,000 EUR
Scientific Officer: Alkmini KATSADA
Research topic: Optimization of methods, systems and primary production chains
Acronym: Bioenergy and food farming systems

One important reason why conventional agriculture is environmentally unsustainable is that it is a net user of large amounts of fossil fuels either via direct energy costs for machinery use or via derived agrochemical products. As such it is far from being an energy-neutral activity.

This proposal attempts to develop a mainstream and productive arable agricultural system that has a minimum goal of energy neutrality. Thus, it will aim to show how it may be possible to integrate, spatially, renewable energy production from biomass crops with low input food crops. It attempts to develop, conceptually, novel combined food and energy (CFE) integrated farming systems that are not only fossil fuel energy-neutral but which also use the biomass crops as ecological reservoirs to enhance biological control within adjacently grown food crops.

The CFE system builds upon principles of integrated crop production taking them further in the direction of energy neutrality in agriculture, reduction of inputs and improved profitability for producers.
The CFE system produces both food and renewable energy, crucially together. Via modelling and experimentation, integrated CFE systems will be assessed for their ecological, financial and environmental economic values, and their balance of renewable and non-renewable energy.
CFE systems with a range of food crops, plus woody biomass for heat and electricity production, will be compared.
Development of CFE systems should improve landscape and land use efficiency.
This proposal also aims to improve the physical and biological diversity of farms their production efficiency and profitability, and lead to waste minimisation with reduced environmental costs thereby contributing to the ecological reform of the CAP.

In this project we will examine and model:

1) how modified land use and management techniques enhance landscape value, biodiversity and biological control by exploitation of natural regulatory components of the ecosystem.
2) the physical and biological properties, nutrient and energy balances, and economic viability of such systems.
3) the complete production and processing cycle of energy crops for heat and power production.
4) the costs and benefits of examples of CFE systems, with and without subsidy support, and in a way that includes external as well as internal cost/benefits.

This project should also provide integrated packages of land use and crop management for alternative production systems. Factors affecting the likely farmer adoptiion of CFE systems will be appraised. With this proposal we highlight the CFE system as a new and integrated farming system which contributes tangibly to increased biodiversity in arable food production.
We integrate horizontally and vertically the distribution of major tasks and sub-tasks between partners and the communication of our results to the wider community.

Current situation/results:
Results show no overall adverse effects of SRC biomass crops on food crop yield or quality as a function of distance. No major disadvantageous food crop/ biomass crop interactions were evident.
Yield mapping showed no pattern of yield change beyond 5m proximity, thus, biomass crops are unlikely to have a negative impact on overall food crop production at the field level.
No adverse effects on the soil environment have been detected. Differences in microclimatic parameters were unlikely to impact on adjacent food crops.
Greater earthworm numbers and species richness was found within the SRC stands, which also support a more diverse assemblage of natural predators. The Carabidae, Linyphiidae and Araneae were the most abundant, especially at crop interfaces, but reductions in pest populations associated with high predator activity/density was not evident.

The Belgium ECOP model accounts for the whole chain of wood production with SRC and electricity conversion at farm level. Profitability was strongly influenced by the reference interest rate, subsidy level, SRC yield, generator power and the price paid for the electricity.
For a financially viable alternative to non-cropped set-aside, SRC must yield > 12odt ha-1 yr-1 and chip prices must be > 60ECU odt-1. Profitability of SRC per se is strongly affected by yield. Large investment costs seriously affect cash flow and hence the Net Present Value, thus there is a need for subsidy. SRC on set-aside gives a better return than non-cropped set-aside, provided chip prices are > 60ECU ODT-1 .
Energy and carbon budgets calculated for typical farms, and whole-system energy analysis show that crop maintenance, harvest and regional transport are most costly, varying with the level of intensification. For yields of 12 t.d.m.ha-1.year-1 at 18 GJ.t-1, the energy content is 216 GJ.ha-1.year-1. The processed wood is gasified to reach 66 GJ.ha-1.year-1. Auxiliary consumption led to a global efficiency of 25% or net production of 63.4 GJ.ha-1.year-1. The SRC-electricity chain has energy balance for wood of 206 GJ.ha-1.year-1 (4.9 ton oil equivalent - toe) and net electricity production of 17.9 GJ.ha-1.year-1 (=5,000 kWh.ha-1.year-1). The energy ratio for wood production equals 21.8 and 1.4 for electricity, compared to energy balance for electricity production using only fossil fuels (diesel) of -228 GJ.year-1 and an energy ratio of 0.28 (< 1; no renewable output). Energy balance of wood and electricity v yield shows that energy balance evolves linearly with yield, ranging from 100-300 GJ.ha-1.year-1 (energy ratio range 14 - 26). For electricity production, energy balance ranges from 6-30 GJ.ha-1.year-1, and energy ratio from 1.2 -1.45. Even with very low yield the energy ratio remains > 1.

There were high-energy inputs with fertilisers, and large variations between food crops (14.03GJ yr--1 - 6.51GJ yr--1). Annual energy inputs to SRC were low (5.23GJ yr-1) and affected by machinery factors. The Energy Return Ratios range from 23 (high yield, all energy used) to 4 (low yield, electricity only).

For an energy neutral system, SRC area requirements range from 7.3% (high yield, all energy used) to 33.6% (low yield, electricity only).


University of Bristol
Long Ashton Research Station
UK-BS41 9AF Bristol
Tel.: +44 1275 39 21 81
Fax: +44 1275 39 40 07


  • Jean-Francois LEDENT
    Université Catholique de Louvain
    Place Croix du Sud 2 - Bte 11
    B-1348 Louvain-la-Neuve
    Tel.: +32 10 47 34 58
    Fax: +32 10 47 34 55

  • John Roy PORTER
    Royal Veterinary and Agricultural University
    Agrovej 10
    DK-2630 Taastrup
    Tel.: +45 35 28 33 77
    Fax: +45 35 28 21 75


  • Adel EL TITI
    State Institute for Plant Protection
    Reinsburgstraße 107
    D-70197 Stuttgart
    Tel.: +49 711 664 24 78
    Fax: +49 711 664 24 98

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