The terms of short and long supply chain have been introduced into the debate over renewable energies chiefly for the purpose of taking into account the impact of logistics and transportation iin the energetic balance.
Typically, on-farm energy falls into the category of short supply chain, while the biofuels tend to belong in the long supply chain, as their production processes depend on raw materials transported at considerable distance, This also implies a different involvement of the farmers. These can be either directly involved in the energy production, or be part of the agroenergy industry as suppliers to industrial energy producers.
The relations between farmers and industrial corporations are not always easy. Farmers don't easily trust corporations either as customers, nor as suppliers. However, there are many good reasons in favour of a constant communication interchange across the industry.
As can be seen from the chart below, not only agroenergy farmers may find in the use of by-products from the biofuels or from the foods industry a cheap alternative to energy crops. They may even find in neibouring industrial sites the customers for the energy (in form of heat or power) they produce. Furthermore, scientific research in agroenergy (e.g. biology) is very often concentrating on the same aspects. Whether in enhancing the fermentation performance of cellulose for ethanol production or in improving the biogas yield of biomasses for anaerobic digestion, all the efforts focus on improving the efficiency of pre-treatments.