|Bioconversion of Organic Residues for Rural Communities (UNU, 1979)|
|Perspectives on bioconversion of organic residues for rural communities|
To identify the most suitable areas in which bioconversion of residues may be important and therefore worthwhile, the residues are divided into three categories, each susceptible to a common method of bioconversion. Cellulose-rich substrates form a total of more than 1,800 million tons annually of renewable resources (Table 1). They are to a great extent found in Asia, and it is therefore not surprising that they consist primarily of rice straw. The present use is often none; in some areas it is used for fuel. Straw could form an extensive base for reeding ruminants. There is no doubt that bioconversion would greatly improve the use of these materials, particularly in rural areas. To what extent in vitro SCP (single-cell protein) production can play a major role here depends greatly on local circumstances and on the results of research efforts in this field.
TABLE 1. Straw Production, 1974 (in millions of tons)
The second major residue category consists of starchy and sugary wastes (Table 2). Because their carbohydrates are more easily accessible, they require a somewhat less difficult form of SCP bioconversion. As shown in Table 2, cassava and sugar beets provide the greatest amount of residue. High productivity in relatively poor soil has made cassava a popular staple food, especially in countries most in need of food.
TABLE 2. Starchy, Sugary Residues (in millions of tons)
A third category of residue is manure, a by-product of all animal production systems. It is calculated that approximately 1,900 million tons of manure are produced per year.