Sustainability of Modern Composting

Composting has traditionally been used as a form of slow rotting of farm-yard manures and vegetative wastes with the resultant humus product useful in agriculture (Balfour; Howard; Wistinghausen & Sattler). However, renewed interest and modern engineering involvement has resulted in an essentially new composting image emphasizing significant technological inputs (Hoitink & Keener, Biocycle; Rynk). A typical example is the use of frequent turning or forced aeration to deliver air constantly to a compost pile. Along with this intensification, there has naturally been a dramatic upturn in commercially available turning machines, in-vessel compost reactors, aeration systems, pile covers, and so on for farms, municipalities and industry. Finally, it is also apparent that there is increased availability to the consumer of a variety of compost-based products. Despite this impressive record of modern composting, little if any actual studies or data exist comparing technology inputs either on the basis of cost/ benefit or quality-of-end products. In contrast, within agriculture in general and specifically in organic and biodynamic farming, numerous comparison studies exist for various alternative management schemes from the viewpoint of cost/benefit, soil-degradation and quality of end-products (Lockeretz). From this point of view, the science of composting appears to lag behind technological developments. Furthermore, the sustainability of intensified composting has never been evaluated. This paper examines certain basic intensification assumptions in modern composting on the basis of economics and process biology. Under consideration is what the effects of varying intensification are in view of nutrient and organic matter retention, endproduct quality and overall costs.