What are biosolids?

Biosolids are a nutrient rich, soil-like product that takes what could be a waste and turns it into a valuable resource that supports sustainable agriculture, forestry, land reclamation, and local gardening.

Biosolids are a beneficial resource made mostly of water, organic matter (plant and animal material), and microorganisms.

How are biosolids made?

Wastewater treatment processes are taken right out of nature's recipe book. In streams and lakes natural aeration helps to purify the water while microorganisms break down solids. Wastewater treatment uses the same idea; the liquid portion is treated and returned to streams, lakes, or oceans, and the solids are further processed into stable organic material, called biosolids.

Everyone contributes directly or indirectly to biosolids. Both businesses and households, whether connected to sewer systems or on septic tanks, generate biosolids. Today, modern treatment processes and strict controls on discharges to sewers contribute to high quality, recyclable biosolids.

Are biosolids the same as “raw sewage” or “sewage sludge”?

No. Biosolids are the end product.

“Raw sewage” and “sewage sludge” are the raw ingredients. Similar to baking, you start with flour but chemical, biological, and physical changes occur as you mix different ingredients and use heat to transform it. You end up with bread. Biosolids are made in a similar way and are the end product, just like baked bread! Only treated biosolids are used on land as a fertilizer and soil conditioner.

How do biosolids work? How does it make the soil better?

Biosolids provide not only organic matter (dead plant and animal material) that helps the soil hold water like a sponge, but also all the essential nutrients that plants need. This includes macronutrients and micronutrients, which makes the product very useful for farmers. Biosolids also store carbon in the soil and help plants take more carbon dioxide out of the air, which helps fight climate change.

The following are benefits from biosolids:

  • Increased crop yields and plant growth
  • Enhanced soil fertility from macro- and micro-nutrients
  • Improved soil organic matter, structure and tilth
  • Increased water-holding capacity in sandy soils; improved drainage in heavy soils
  • Reduced soil erosion from wind
  • Increased diversity and productivity by soil microorganisms
  • Improved habitat (food and cover) for wildlife

What are biosolids used for?

Biosolids are used on farms, forests, landscapes and gardens, and to reclaim degraded land and old mine sites.

Biosolids provide essential nutrients for sustainable agriculture and healthy crops.

In the forest, biosolids increase forest productivity, increase tree growth, and improve wildlife habitat.

Composts and soil mixes made with biosolids, usually mixed with sawdust, wood chips, bark, yard clippings or crop residues make excellent mulches, composts, and topsoils for gardening and landscaping.

In land reclamation, biosolids are used to replace lost topsoil, where they improve soil fertility and stability and help revegetate the land and decrease erosion.

Do biosolids smell?

Composted biosolids usually don’t have much odor, they tend to smell like any earthy potting soil or mulch.

Soil mixes with biosolids tend to have a little bit of smell.

Straight biosolids can have an odor that is similar to bone meal or manure, an earthy, ammonia, and Sulphur smell. This is the smell of essential plant nutrients! After being worked into the soil, the odor usually goes away quickly.

What do biosolids look like?

The way biosolids look depends on the treatment process. Some biosolids are mostly solid, spongy material, and some are liquid. Some are dark, almost black, and some are reddish brown like clay. Some biosolids have sparkles in them, called struvite (a mineral).

Can I eat food grown with biosolids?

Yes! Biosolids are applied in amounts that meet the exact nutrient needs of the crop, and are kept far away from streams, wetlands, wells, and other sensitive areas. Research shows food grown with biosolids has more protein and higher yields than food grown without biosolids, and contains no harmful chemicals.

A recent risk assessment by Kennedy/Jenks and the University of Washington found that you would have to work with biosolids for many, many lifetimes before you would even get one dose of ibuprofen. Most of us won't live that long! Scientists couldn’t find any pharmaceuticals in wheat grain that was grown with biosolids.

Has any research been done?

Biosolids is one of the most heavily researched soil conditioners/soil amendments available. Decades of research have informed the way biosolids are made, used, managed, and regulated by the Environmental Protection Agency. Thousands of peer reviewed articles by reputable university scientists repeatedly demonstrate that biosolids create numerous environmental benefits and protect public health.

In an independent study, the National Academy of Sciences reviewed current regulations, management practices, and public health concerns and concluded that "the use of these materials in the production of crops for human consumption when practiced in accordance with existing federal guidelines and regulations present negligible risk to the consumer, to crop production and to the environment."