The fruits and vegetables harvest and transformation processes yield many wastes: trimmings, hulls and shells. In 1995, the US Department of agriculture estimated that over 250 million dry tons of agricultural crops and residue were generated over a year in the country [23]. The chemical composition of agricultural crops and residues is very similar to that of perennial herbaceous plants (see Sect. 11.2.1.4). The interest in these feedstocks is reflected in the abundant literature found on agricultural crops and residues pyrolysis [24-26].

11.2.1.5 Animal Manures

Animal manures are used as fertilizers: their high urea, phosphorus and organic con­tents enrich soils dedicated to agriculture. Cattles are the main manure producers with production of over 200 million dry tons a year in the US (commercial broilers are showing comparable numbers) [23]. Because manure has a heterogeneous com­position, thermal decomposition has gained interest to recover that feedstock. Cattle manure is more difficult to collect than poultry manure [10]. Therefore, poultry ma­nure is considered as a good candidate for industrial pyrolysis, and the scientific literature has been mostly focused on this type of manure.