Biosolids

Using biosolids in your yard: Health and safety questions and answers

Biosolids: A recycled organic fertilizer

Using biosolids in your
yard: Health and safety
questions and answers

Stewardship gardening links outside WSU

Are biosolids available for private yards or gardens, and if so, is there any problem using biosolids on vegetables or around children?

Some municipalities give biosolids away or sell it to the general public for landscaping or gardening purposes. Biosolids used around home must be treated by a process to further reduce pathogens such as composting, heat treatment or thermophilic digestion. In some places the biosolids are composted with sawdust or other bulking agents and sold as a topsoil or soil amendment. Biosolids compost makes an excellent mulch, soil amendment and substitute for manure composts, peat moss and other elements used in soil mixes. Class A biosolids may be used for landscaping and gardening purposes, however, when growing food crops with biosolids it is recommended that the user maintain the soil pH at or above 6.0. Keeping the soil pH at this level immobilizes the trace metals in the soil, minimizing absorption by plants.

Can land application of biosolids transmit trace metals and thereby endanger human health?

Of the various metals found in biosolids, cadmium and lead are of the greatest concern to human health. The greatest accumulation of cadmium in the food chain is in the leaves of certain plants and in the livers and kidneys of animals that live in or near the soil. Research has shown that lead does not accumulate significantly in plants and into the organs of wildlife such as deer. It was also found that lead levels were not elevated in blackberries grown in the treated forest. Cadmium does accumulate in plants, particularly in leafy vegetables and root crops. EPA risk assessment for vegetables grown in biosolids-amended soils shows no significant health effects from eating these vegetables when the trace metals in the biosolids have been applied at regulated rates.

Could a person inhale airborne bacteria or viruses when biosolids are handled or applied?

Gardeners must always use common sense when handling any chemical, fertilizer, manure, or even garden soil. Research has shown that Class A biosolids contain no pathogens.

Back to Biosolids: A recycled organic fertilizer

More information about this topic is available through your local Cooperative Extension Office.

Source: James A. Kropf, Extension Faculty, Horticulture, Small Farms and Farm Marketing. (1998)