Biosolids are nutrient-rich soil-like material created when sewage from homes and businesses is cleaned at wastewater treatment plants. During treatment, the solids are separated from water and go through processes that remove harmful germs. The result is a safe, organic fertilizer that can be used by farmers, ranchers, and land managers to boost crop yields, improve soil quality, reduce the need for water and chemical fertilizers, and adapt the land to climate change. 

Biosolids are strictly regulated and must meet protective Environmental Protection Agency (EPA) and California environmental requirements.

Benefits of Biosolids

Biosolids are a powerful natural resource that have benefits for the planet and people. Biosolids help:

• Biosolids return nutrients and organic matter to soil that would otherwise go to a landfill.
• Biosolids improve soil structure which helps it to retain water and nutrients, making the land more resilient to erosion and drought.

• By adding nutrients and improving soil quality, biosolids increase crop quality and farm yields.
• Biosolids supply all essential nutrients crops and plants need, including nitrogen and phosphorus.

• Biosolids contain significant amounts of carbon-rich organic matter that gets trapped in the land, versus warming the planet in the atmosphere.
• Biosolids reduce the need for synthetic fertilizers, which require an intense amount of fossil fuels for production.
• The most common biosolids treatment process, anaerobic digestion, naturally produces methane gas, which can be captured and used as a 100% renewable energy source.

• When applied to land ravaged by wildfires and mining operations, biosolids replenish nutrients, encouraging plant re-growth and stabilizing slopes.

• As a low-cost alternative to synthetic fertilizers, biosolids provide cost savings to farmers, ranchers, and land-managers and improve profits by increasing yields.

How are Biosolids made?

Biosolids turn “waste” into a valuable resource. This saves space in landfills, reduces the need for chemical fertilizer, and returns nutrients to the soil.

The cycle starts with the food we eat. What our bodies don’t use gets flushed down the toilet and travels through sewer systems to a wastewater treatment plant. At the treatment plant, solids are separated from wastewater. The wastewater is cleaned and safely released to the Bay. 

The solids are then heat-treated in large tanks called anaerobic digesters, where microorganisms break them down. This process kills disease-causing organisms and pollutants. The result is a safe, nutrient-rich soil-like resource called biosolids.

Biosolids are closely monitored through laboratory testing to make sure they meet strict safety standards.

Biosolids are transported to farmers as a more sustainable alternative to chemical fertilizers. In California, typical crops grown with biosolids are hay and forage grasses. These crops are used to feed animals, which create food for humans… and the cycle begins.

Biosolids are Not Poop!

Your poop is the raw material that ends up at a wastewater treatment plant. Biosolids are what your poop becomes after it’s treated and meets strict safety regulations.

Are biosolids safe?

Yes. The safety of biosolids has been studied for more than 50 years and is supported by research from the Environmental Protection Agency (EPA), United States Department of Agriculture (USDA), the U.S. Food and Drug Administration (FDA) and top universities across the United States and Canada. Biosolids are always tested to confirm they meet federal and state requirements for safety. They are regulated much more intensely than synthetic fertilizers, manure, and compost. Today, in California, approximately two thirds of biosolids that are created are applied to soils, and they have been widely used on farms and other lands across the U.S. for decades.

There are many misconceptions about the safety of biosolids. Here are the facts:

Biosolids do not content high levels of heavy metals 

California’s mandatory pre-treatment programs prevent industries and manufacturing facilities from discharging metals into sewers. The metal content of biosolids is typically very low. The concentration of heavy metals in biosolids is similar to that found in natural soil, manure, or compost.

Biosolids do not contain harmful levels of pharmaceuticals

Biosolids contain extremely low amounts of pharmaceuticals, as the majority of pharmaceuticals are broken down during the treatment process. Research and risk analysis demonstrate that it would take many lifetimes of working with biosolids to equal everyday exposure to many common products. For example, a person would have to farm or garden with biosolids for over 20,000 years to take in the equivalent of a single tablet of ibuprofen.

Biosolids are not a main source of exposure to Per- and polyfluoroalkyl (PFAS) 

PFAS are a class of harmful chemicals found in an abundance of household products we use everyday. PFAS are so common in our environment and the products we interact with, that studies have shown that most adults have some levels of PFAS in their blood. Unfortunately because of this, they end up in our wastewater system and therefore can be found in trace amounts in biosolids. However, the amount of PFAS found in Bay Area biosolids is extremely low.

In some parts of the United States, a few wastewater treatment facilities have been found to have higher levels of PFAS due to manufacturing facilities in those communities. There are no PFAS manufacturing facilities in the Bay Area. 

Human exposure to PFAS comes mainly from everyday household products like non-stick cookware and waterproof and stain-resistant textiles, not biosolids. The FDA has not found PFAS in 97% of food samples (both fresh and processed) since it started testing for them in 2019. Only two out of 3,200 meat and poultry samples tested by the USDA had detectable levels of PFAS.

Below is a graphic showing relative amounts of the two most common PFAS chemicals, Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA), measured in various substances, including Bay Area biosolids (“SFPUC Biosolids”). 

BACWA and our member agencies are working hard to reduce PFAS entering the wastewater system in the first place by reducing PFAS at the source: we are advocating for the regulation of the industries that are producing products with PFAS.

You can help! By making informed decisions about the kinds of products you buy and use at home, you can reduce the amount of PFAS that gets washed down the drain and encourage industry to not use these harmful chemicals. Look for PFAS-free labels when you shop. Here are tips for finding PFAS free products.

Another way you can help is to ask your state and federal elected leaders to ensure that the “polluter pays” when it comes to addressing PFAS, so that the companies that manufacture and profit from PFAS are the ones that bear the cost of PFAS cleanup, not your local utility or you as a customer.

The Bottom Line on Biosolids

Clean water agencies are among our community’s biggest protectors of health and the environment. They work 24/7 to project your health, reduce waste, and keep our Bay and waterways clean.

Biosolids are a useful byproduct of the wastewater treatment process. Instead of creating waste that must be disposed of, we create a nutrient-rich product that brings many benefits to communities. Biosolids are safe, effective, and sustainable.