PERSPECTIVE

Compost Science & Utilization, (2008), Vol. 16, No. 1, 3

Adding Value To Compost Processes And Products

THE selection of papers in this issue of Compost Science & Utilization illustrates the level of sophistication and knowledge with regard to composting and compost use. From results of testing a new method for assessing stability to enhancing production of a fungus inoculum in a mixture of

compost and vermiculite, the research community is adding value to compost processes and products.
The initial paper compares standard analyses for measuring compost stability such as C, N, and microbial respiration, to neutral detergent fiber and lignin content - predictors of N mineralization or immobilization from raw and composted dairy manures. Researchers found that microbial respiration and fiber analysis can be used to establish relative differences in compost stability.
Another study evaluated the effects of adding five rates of powered elemental sulfur or ferrous sulfate on the acidification process of three alkaline composts made from residual vegetable crop biomass. A drop in compost pH following sulfur amendment occurred, as did a “remarkable increase in autotrophic bacteria population and a slight increase in heterotrophic bacteria,” report the authors. Amended composts showed a range of physico-chemical and chemical characteristics suitable for use as growing media ingredients for containerized crops.
An especially timely paper in this issue discusses food waste composting with selected paper products. The number of programs being established to compost source separated food wastes is growing rapidly around the world. Many of these programs incorporate compostable products and food-soiled paper. Much of the scientific research on compostability and degradability of these products has been conducted at the laboratory scale. Note the authors, “there is still the need to conduct trial studies to understand the performance of the composting process and the quality of finished compost in the presence of biodegradable paper products in food waste composting.” Specific objectives of this study were to compare the degradation of three different paper products (regular food service plates, a commercial biodegradable paper product and Earthshell-made plates) in the composting process; monitor changes in materials during composting (e.g., particle size, pH, chemical composition); and conduct greenhouse pot experiments with the finished compost.
The three final papers in the issue all relate to some aspect of compost utilization. They include evaluating the effect of vegetable, fruit and garden (VFG) waste compost on soil physical properties, choosing a mixture ratio for on-farm production of Arbuscular mycorrhizal fungus inoculum, and experimental use of composted grape seed and olive mill residues for amelioration of fertility and structural stability of soils. In the case of the VFG compost, the authors report that combined application of the compost and cattle slurry resulted in the best soil physical conditions. Authors of the paper on AM fungi provide equations that allow a farmer to choose a mixture ratio for on-farm propagation knowing only the nutrient analysis of the compost to be used. In the final paper, the researchers from the University of Girona in Spain found that compost application improved soil aggregate stability, optimized water retention and produced a net increase in soil respiration.
Taken all together, the research findings reported in this issue add significant
value to the composting knowledge base - as well as the processes and products. - Jerome Goldstein

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