Compost Science Complete scientific data on compost process control and end product quality

PERSPECTIVE

CSU Summer, 2005, Vol. 13, No. 3, p. 159

Diversity Thrives 'Round The Compost Concept

FROM RESEARCHERS in the Departent of Environmental Engineering at Hokkaido University in Sapporo, Japan come insights into the moisture content inside the composting process of a biotoilet system. (See page 208 of this issue.) Richard Koenig and his colleagues at Washington State

University and Utah State University provide data on the variability of atmospheric ammonia in high-rise, caged layer composting facilities. (p. 162) From Barcelona, Spain, we learn that the wine industry in Catalonia is critical to the economy there, with the Miguel Torres S.A., a well known company generating significant amounts of liquid and solid organics as part of its production of high-quality wines and brandy. (p. 168) Meanwhile, a team that includes horticultural scientists from Oklahoma State University, Florida Indian River Research & Education Center, and the Soil & Water Science Experiment in Gainesville, Florida are seeking to replace a peat medium with compost for transplanting cauliflower. (p. 175) These topics are only some of the papers which you are about to read in this issue of Compost Science & Utilization. And so the knowledge base builds, critical answers come forth, and growers - and consumers - benefit greatly.
Let's spend a little time in the Japanese community of Sapporo with the biotoilet system. The biotoilet is the name of a dry or composting toilet that uses sawdust as a bulky matrix for bioconversion of human excreta into compost which can either be used as organic fertilizer rich in N, P, K, or as a soil conditioner. The composting reactor of the biotoilet system is provided with heating and mixing systems that ensure a continuous thermophilic aerobic biodegradation process and a uniform temperature distribution. Moisture content in the reactor is kept in the range of 50 to 60 percent by heating and ventilation; the system is designed to accelerate decomposition and minimize odors.
Optimum moisture content represents a tradeoff between moisture requirements of microorganisms and their simultaneous need for adequate oxygen supply. Water is the key ingredient that transports substances within the composting matrix and makes nutrients physically and chemically accessible to microbes. The wide ranges of optimum moisture content indicates: 1. The complex dynamic nature of the composting process, with changes in particle size and structure occurring over the time; and 2. The necessity of more fundamental and inclusive parameters for understanding the physical and biological interactions controlling the composting process.
As explained by Zavala and Funamizu, the composting process in the biotoilet system differs from that in conventional composting systems. Understanding how the moisture content affects the rates of aerobic biodegradation of feces in the biotoilet reactor is a key factor for setting criteria for proper design and operation, and for achieving the system goals.
Meanwhile, back at the winery in Catalonia and recycling pomace, wine sludge and sediments, organic fertilization has a critical role in wine quality and sanitation. Stalks are an excellent bulking agent for wine sludge composting, due to physical properties such as porosity and resistance to biodegradation. Cocomposting wine sludge from the wastewater treatment plant with stalk as bulking agent generates a stabilized fertilizer suitable for vineyard crops. The process even allows for treating different wood wastes - such as ground old oak barrels - as part of the feedstocks. Once again, we witness an industry that has come to excellent grips with a sustainable waste management strategy. And that - as we like to say in the halls of our editorial offices here at CS&U - is what we're all about as we move 'round the compost concept. - J.G.