FAQs

Why not compost our food waste aerobically, similar to what I do in my backyard, but at a region-wide scale?

Like home composting, large-scale (municipal) food waste aerobic composting facilities require woody debris (biomass) to absorb moisture and provide the proper environment for the aerobic microorganisms to function. A successful municipal-scale composting process typically requires two to three times more woody debris than food waste depending on how wet the food waste is. In Humboldt County, we have two (sometimes three) biomass plants that convert woody debris to electricity; therefore, this resources is currently being absorbed by other industries. The Foodwaste to Watts program is designed to be a service that provides a solution for a currently wasted resource and does not seek to redirect products to our facility.
A portion of the County’s yard waste (wood debris) does come to the HWMA facility; HWMA currently receives and processes about 4,500 tons per year. Why don’t we use this for aerobic composting? According to a recent Humboldt County Waste Characterization Study, there is about 13,000 tons of food waste in out waste stream. If we wanted to try to compost even half of that (~7,500 tons), we would need 14,000 tons of woody debris (using the 2:1 woody debris to food waste ratio). Therefore, to aerobically compost Humboldt County’s food waste, HWMA would have to import and pay for wood chips i- this is not inline with our project goals, and would not be economically viable!
Finding a site for a food waste aerobic compost facility is very difficult due to perceived and actual impacts. Many people do not want such a facility “in their backyard” as they worry about increased odors and trucking traffic. In 2006, HWMA searched for a site to construct a yard waste compost facility; seven (7) sites were evaluated and all were rejected for both residential concerns and permitting issues. HWMA was successful in securing its current yard waste composting facility (located at Wes Green Landscape Materials) only by ensuring that food waste would not be processed at the facility; this permitting requirement stands today. Why not try to find a site away from population centers? This would require additional trucking to get the materials onsite, then more trucking to get the finished compost product back to the people/consumers. This additional trucking would not only increase the cost of the compost program, it would also increase greenhouse gas emissions associated with waste diversion- this is not inline with our project goals!
Recent research indicates that aerobic composting processes that contain food waste can result in greenhouse gas emissions (methane and nitrous oxide), and an increase in Volatile Organic Compound (VOC) emissions. Additionally, food waste composting relies on heavy equipment that uses diesel fuel. This adds to the overall greenhouse gas emission associated with aerobic composting. Conversely, anaerobic digestion takes place in a fully contained vessel, and relies mostly on electricity produced by the vessel itself!
Aerobic composting only generates revenue by selling the finished compost product to consumers. This product has a limited market. Conversely, anaerobic digesters generate revenue by selling renewable energy and finished compost! The key difference here is the fact that aerobic composting releases the energy in food waste in the form of heat; anaerobic digesters convert food waste into methane that can be used to produce valuable products such as electricity, heat, and vehicle fuel.

Is it OK to continue my backyard composting practice?

HWMA supports backyard composting. This is a part of the solution to increase waste diversion from landfills. However, there are many people who live in apartments or other housing without backyard space making aerobic composting very difficult or impossible. Further, some people report that they simply don’t have the time for or interest in backyard composting. For those people, HWMA is providing this waste diversion solution.
HWMA applauds backyard composting efforts! However, many people have poorly maintained compost piles that cause odors, attract rats, raccoons, skunks and other vectors for spreading disease. More importantly, these under-turned piles are producing methane and nitrous oxide – two very powerful greenhouse gas emissions. HWMA’s Foodwaste to Watts program has been created to reduce harmful gas emissions into the atmosphere.

Is the Foodwaste to Watts program going to take food away from local food banks?

Absolutely not. Food banks only accept food that is fit for human consumption. They are well established, and are already collecting food from the available sources. HWMA is targeting the food that ends up in the trash. If during the development of this project we come across other sources of food fit for human consumption, we will make sure that the food banks are notified.

Why not put all food waste down the garbage disposal?

Putting food waste down garbage disposals increases the organic material and quantity of water (hydraulic loading) at waste water treatment plants. If everyone put leftover food waste in their sink disposals, residents would have to invest in expensive waste water treatment plant upgrades to handle the additional materials. In fact, many cities have banned the use of sink disposals for this reason.

Is getting food waste (organics) out of the current waste stream really a big deal?

Yes! Food waste creates a source of uncontrolled methane (a powerful greenhouse gas) in landfills; it is the second largest source of man-made methane contributing to climate change.
Food waste is heavy as it contains about 75% water. When Humboldt County haulers take this to the landfills, we are effectively using diesel fuel resources to haul water 180 miles!
Food waste is the largest remaining component in our waste stream. By diverting and locally processing food waste, not only do we increase the amount of waste diverted from landfills, we keep more of our waste dollars in the county. This will help to stabilize waste management costs, create local jobs, and reduce emissions from trucking and landfilling.
When we send our food waste out with the trash we are losing valuable nutrients that are needed to grow more food! By processing this waste locally, recycled nutrients are captured and placed back on our fields, reducing our demand for fossil-fuel derived fertilizers.

Can I get food waste collected at my house?

Yes, but not immediately. HWMA plans to begin collecting food waste from the commercial sector such as restaurants, hotels, and schools. We foresee collecting food waste from residential areas during the second phase of the program. If you would like this service, let your local city council know! HWMA would like to collect from residents as soon as possible; if people demand this service it is more likely to be offered sooner than later.

What happens to the food waste after it is collected?

Food waste will be taken to a pre-processing facility where it will be reduced in size (ground up) and contaminants will be removed. Then, food waste will be loaded into the anaerobic digester where it will circulate for about 28 days. During this time the anaerobic microorganisms will convert the food waste into three products: 1) methane, 2) carbon dioxide, and 3) a stabilized organic soil amendment. At this time, the volume of solid waste will be reduced by more than half. Once the digestion process is complete, captured methane will be converted to electricity and sold to generate revenues to keep the cost of food waste processing low. The stabilized organic matter will be mixed with green waste compost and sold to local consumers.

Why can’t all foodwaste be used for animal feed?

Food waste from several local restaurants currently goes to feed pigs in the County; however, there are simply not enough pigs to absorb the entire County’s food waste! More importantly, California Department of Food and Agriculture law requires post-consumer food waste to be heated to 212 F for two hours. This pre-treatment adds considerable cost to the otherwise free pig food.
Postconsumer food waste is contaminated with non-food items that would add more cost to the farmer. Finally, pigs won’t eat everything, and produce a high-strength waste that then needs to be treated.

What is anaerobic digestion?

Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and pH levels can be controlled to maximize microbial populations, gas generation and waste decomposition rates. Anaerobic digestion has been in use for several decades to treat sewage sludge, animal wastes and industrial wastewater. Only in the past decade, has the technology become a recognized method for processing solid organic waste from residential and commercial sources. The benefit of an AD process is that it is a net generator of energy which can be sold off-site in the form of electricity, heat, or a vehicle fuel. Additional benefits of using AD for municipal food waste are that digesters are flexible in terms of what types of waste they can handle. For example food waste digesters can handle very wet waste streams such as cheese whey, shrimp guts, and grease trap waste, as well as food soiled paper products. Digesters have a small footprint, and a short processing time compared to composting.

What types of organic waste can go into the anaerobic digester?

All Food waste (veggies, meat, dairy, etc.), Grease trap waste, Shrimp guts, Crab guts, Food soiled paper (i.e., pizza boxes, napkins etc.), Cheese whey, Spent brewer’s grains, Coffee grounds, and Manure.
Anything that stinks or goes bad.*Exceptions to this rule are doggie doo – and baby poo (diapers) – while the anaerobic digester can process these wastes, there may be health and safety risks associated with processing excrement that need to be investigated before including them in our system. Also diapers contain a lot of plastics and other materials that can add to the complexity and cost of pre-processing this material.

What is the difference between pre-consumer food waste and post-consumer food waste?

Pre-consumer food waste is waste that has not been served to customers. Examples are the cuttings from food preparation and unserved food. Post consumer food waste is all waste that has passed into a customer’s hands.