COMPOSTING: Minnesota Takes Aim At Compost Standards

George Johnson Steve Crawford

Composting is not new to Min-nesota, a state with more than one-third of the country's compost systems and a considerable amount of operational experience.

Minnesota's composting facilities have the potential to generate more than 100,000 tons of compost annually. The state has to examine composting aspects and consider the diversity of municipal solid waste (MSW) feedstocks, processing technologies and end uses.

Evaluating composting alternatives brings forth a number of fundamental scientific questions such as, the physicochemical and biological quality of compost and appropriate uses for the material.

To help develop markets for MSW compost, the Minnesota Office of Waste Management (OWM), St. Paul, Minn., formulated the Com-post Utilization Program (CUP). CUP is used to guide research and to demonstrate the use of MSW compost in various applications. This work is being performed by three principle investigators at the University of Minnesota.

CUP also can characterize the product quality of all MSW composts produced within the state. The OWM hopes that CUP will minimize the uncertainty of compost quality and its chemical characteristics.

To date, no United States composting products have been tested using consistent material sampling and analysis techniques. This lack of uniformity has therefore made it difficult to compare compost analytical results between various facilities.

Financial assistance is available for companies interested in studying compost products. This year, for example, the OWM awarded Stillwater Inc. a $250,000 grant to evaluate the quality of compost produced at Minnesota's facilities. In addition to this, the National Composting Council, Proctor & Gamble and Buhler have offered additional technical and financial assistance to the CUP project.

In the two-years allotted to research CUP, the research objectives included: to characterize the compost produced at all Minnesota MSW composting facilities; help to develop markets for the finished compost material; investigate real and perceived environmental risks from compost use; determine the benefits/cost of compost production and; using learned data and provide technical assistance to the Minnesota facilities and other composting operations.

The first CUP quarterly reports have been submitted to the OWM for review. According to preliminary results, existing analytical techniques need to be modified and more research is necessary in additional areas.

The report concludes that Minnesota facilities produce finished compost with significant differences in product quality. The compost's quality is affected by variations in feedstock, processing and storage methods, seasonal variations, and sampling techniques.

Finally, once chemical contaminants are mixed with compostables, it becomes extremely difficult and expensive to remove the toxic components from the final compost.