The use of steam treatment to upgrade lignocellulosic materials for animal feed
Lignocellulosics (LC) are the most abundant and under-utilised renewable resource of energy in the world. The present study is concerned with finding alternative uses to LC as an animal feed using environmentally friendly technologies. The major biological constraint for using LC is related to the low accessibility of cell wall polysaccharides to both cell-free and microbial enzymes. This can only be overcome by some type of processing. This study emphasises the use of physical (steam) and biological (enzymic) treatments. Results have shown that both low (LT) and high temperature steam treatment (HT) are efficient methods for solubilising hemicellulosic sugars and depolymerising lignin. However, HT leads to higher losses of both sugar and dry matter. Higher improvement in fibre bio-availability was obtained with HT and yet, this effect was more evident from enzymic hydrolysis data compared to rumen fermentation. LT can be used for upgrading LC since exogenous chemicals are added. HT showed to be an attractive alternative for producing animal feed and substrate for enzymic saccharification without requiring chemicals. The effects of steam treatment on fibre physical structure were particularly important. Greater effect was noticed under HT in combination with rapid decompression. It was suggested that rapid decompression should be avoided in the context of animal feeding. Experiments on toxic compounds indicated that furans have negligible toxicity to rumen micro-organisms. Phenolic compounds, however, are potentially toxic and can affect the pattern of rumen fermentation, gas production and adhesion of bacteria to substrate.