Sonoma Compost--Garbage into Gold
An interview with Will Bakx of Sonoma Compost
By Lyn Gannon, Sonoma County Master Gardener
Last time I went to the landfill, I expected to toss my garbage off an embankment as I had years ago. Not any more! Now garbage is dumped on a concrete floor in a large shed, loaded into huge trucks and hauled away. I’d read that Sonoma County landfills don’t accept garbage any more, but I hadn’t grasped that we export it now! That knowledge - like no other - changed my perspective about re-cycling and got me thinking about yard trimmings.
To “get the dirt” on how garden debris gets turned into compost, I met with Will Bakx. He is one of two owners of the organics recycling center, called Sonoma Compost Co., at the County’s Central Site Landfill off Meacham Road in Petaluma. Bakx, who hails from The Netherlands, has an MS degree in soil science, and has been in the compost producing business since 1985. He’s also been teaching composting class at the Santa Rosa Junior College for the last 3 years.
Sonoma Compost originated as a local business in Bennett Valley and moved to its current location in 1993. By then, California law required landfills to halve their waste stream by 2000. After a successful one-year pilot for the City of Santa Rosa, the company was awarded the contract to implement the county-wide program. And Sonoma Compost has been turning garbage into gold ever since.
Sonoma Compost is one of the largest green waste recycling programs in the State. On an average day, the facility processes 250 tons of yard debris! And, since the center was started, it has diverted over a million tons of yard trimmings and wood from the landfill. Without this facility, we would be shipping our yard trimmings out of County, too.
The facility is an impressive sight. Located on 18 acres, it’s covered with windrows (elongated piles) of yard trimmings. A steady stream of vehicles – from pickups to large trailers – brings in the raw materials and takes out the finished products. In 2008, Sonoma Compost was awarded the California Legislature Assembly Certificate of Recognition – Sustainable North Bay Award for their contribution to the local environment. For more details, see the web site: www.sonomacompost.com
Here are some highlights from my chat with Will:
MG: Could we start with you defining the term “green waste”?
WB: Well, I’d like to start by saying that I try to avoid using that term! (laughing)
MG: Oh, no!
WB: The words we use when talking about re-cycling are important. I only use the word “waste” when material is truly wasted. We want to think beyond the “garbage mentality”, which perceives of everything that we no longer use as garbage. Only then can we see the possibility of extracting something of value from something seen before as waste.
MG: You’re saying that we need to clearly differentiate between what is re-usable and what is waste?
WB: Exactly. As a re-cycling facility, our goal is to extract a resource out of our waste stream. Technically, we are an organics recycling center, meaning everything we process is either compostable, made into mulch, prepared for green energy, or sold as reusable lumber. The materials we process are also called “yard trimmings” or “yard debris” and “wood discards”.
There is some confusion about the term “organic”. When we refer to something being “chemically organic” that means it has the structure of a carbon chain. Then, there’s the term “organic” which applies to the method used to grow crops. Our products are organic according to the first definition because they are made out of carbon-based materials. And, most of our products are also “organic” according to the standards set by the Organic Materials Reviewing Institute (OMRI), which certifies which food products can be labeled as organic. As a result, all our materials - except for the path mulch - can be used by certified organic farmers.
MG: How do you insure that your products are “organic” from the food perspective?
WB: We start by keeping yard trimmings separate from the rest of the waste stream (source separation) – we even remove wood products. Not all facilities work that way; some receive their re-cyclable garden materials already mixed with regular garbage. But if materials are mixed, then there’s no way to determine if motor oil or other chemicals have been absorbed by the green materials. For that reason, we closely monitor what we receive.
Even then, we still have to sort through materials once they arrive. For example, we do not allow wood products such as lumber or building materials to mix with any products which will eventually be labeled organic. Removing plastic bags before we start the composting process is a constant challenge, too. In fact, whoever invented the lawn bag, should be out here helping us remove them from the materials we receive! (laughter) Here is Sonoma Compost Guide to Acceptable Materials
MG: Let’s talk about that for a minute…
WB: Plastic bags are the biggest contaminant that we have. Many people think they are helping the environment when they put plastic bags labeled “compostable” in their green cans. But compostable bags do not meet OMRI’s or other organic standards. Even though these bags are made from corn (or other plant material), chemicals are added to change corn from a syrup to a synthetic polymer. And materials used to grow certified organic products cannot contain synthetics.
MG: Does that mean that Sonoma county residents should be re-cycling compostable plastic bags with our glass, cans, cardboard, etc?
WB: Believe it or not, compostable plastic bags are not recyclable here! At the moment, they are truly garbage. Unfortunately, the same material is used to make cups, and plastic ware. And these products are expensive, too.
MG: Would you mind returning to the point you made earlier about learning to look differently at what we discard as recyclable rather than waste? Are you advocating that we focus on using what we’ve already accumulated, instead of finding the fastest way to get rid of it?
WB: Yes, we need to develop new habits of using only what we need. Actually our environment will also benefit if we look beyond re-cycling as the only solution to minimizing our footprint. To some degree, the concept of re-cycling can backfire. Anything we use and recycle still has energy expenses associated with manufacturing and transportation at one end and re-cycling and transportation at the other. So even though we sell compost materials, I still encourage residents to compost as much of their garden trimmings as possible. Finding ways to re-use materials generated on our own land makes the most sense because it reduces the transportation factor.
Home gardens can be developed with low carbon footprints by reducing fertilizers and pesticides. In contrast, the whole fertilizer and pesticide industry is based on the idea of produce, produce, produce. But it also means that we trim, trim, trim and haul, haul, haul. A different approach could benefit the environment and reduce maintenance for homeowners. Finally, we can do more than find alternatives to expansive lawns; we can also consider growing more plants in home gardens that produce food.
MG: As a gardener, I tend to feel guilt-free about filling up my “green” can since yard debris can be re-cycled. I had never considered that processing yard debris has a cost.
WB: The order of the words in the slogan “Reduce, re-use, recycle” is important. Reduce waste as much as possible, re-use as much as you can, and then finally recycle as a last resort. For example, we apply those principles at our facility by sorting used wood. We set aside and sell re-usable lumber, and we sell any firewood we receive “as is”, rather than grinding it up. We grind up only the wood that cannot be re-used.
MG: Well, looking outside at the size of your operation, I’m wondering - do all these raw materials come from Sonoma County? You have dozens of windrows (rows of compost).
WB: Yes, Sonoma County residents produce all these materials. And at our site, we have an average of 18,000 lineal feet of windrows - 7’ high and 18 feet wide – composting at one time.
MG: That’s a lot of material! Do you also get materials from local agricultural sources?
WB: A little bit. We get some grape pomace, manure, and some other animal by-products. For example, we recycle feathers to increase the Nitrogen content of our compost.
MG: I’m curious. Are you on the lookout for other materials so that you can increase the scope of what you re-cycle here? Or, do you have enough on your plate?
WB: We are close to capacity, yet I am always looking for other materials which we can avoid treating as garbage. About a year and a half ago, we started accepting food waste – fruit, vegetables, even bread, pasta, and egg shells can go in green cans right now. Food waste still accounts for about 80,000 tons/year in the waste stream. Even though this material is biodegradable, if it is not recycled, it is still going into the landfill.
MG: That is a lot material which could be diverted. It’s easy to think that food I toss in the garbage at home is inconsequential. But when multiplying that amount by the number of homes in Sonoma County, that number does become significant.
WB: It does!
MG: Are the products you sell available to people outside of Sonoma County?
WB: We sell a considerable amount to Marin and Mendocino Counties, though our focus is Sonoma County. Our motto is “sell locally”, so we don’t add transportation to the impact. We also have some restrictions because we are in a SOD (Sudden Oak Death) Area. Even though the pathogen causing SOD is killed in the composting process, we are still under quarantine. As a result, we’re only allowed to sell in SOD affected Counties. That means we can sell as far North as the Oregon border, but cannot ship to the Sacramento Valley.
MG: One of the things that I like about this facility is that I can drop off a load of yard trimmings and then pick up a load of compost and mulch on the same trip.
WB: We encourage people to do that to reduce the carbon footprint. True re-cycling means that you not only getting rid of your yard trimmings, but close the loop by bringing it back in another form.
Plus, you get a 15% discount coupon if you tell the gate attendants when you drop off a load that you’d like to pick material up as well.
MG: Earlier you mentioned that you keep your piles free of contaminants by monitoring and restricting what goes into them. How do you ensure that your piles are free of pesticide residues if you accept yard trimmings from so many sources?
WB: We start by inspecting all trucks that come in here for contents that don’t meet our criteria. The “self-haul” people clean their own loads by removing plastic bags; this quickly trains them to bring clean loads! Occasionally, a truck comes in with garbage left in it before picking up yard debris; those loads are rejected.
As far as pesticides are concerned, we have to assume that we receive materials that carry pesticides. Pesticides break down during the composting process. They are composed of a carbon chain with functional groups attached to it. From a microbe’s point of view, a pesticide is no different than a loaf of bread. Some pesticides decompose faster than others; it depends on their makeup. Nonetheless, we test samples of our products monthly for pesticide residues and typically come back with a clean bill of health.
MG: How about heavy metals?
WB: Running a clean operation from the start, eliminates problems with heavy metals. Most of the problems arise at facilities which compost wood with their yard debris. Incidental pieces of pressure treated wood can ruin your whole batch. Good separation of yard trimmings and wood is key. And, we test samples of piles before they are sold to make sure the material is safe.
MG: From talking with other gardeners, I know that many are looking for sources which will guarantee their products won’t be contaminated with weed seeds, diseases and insect larvae. How do you address that?
WB: Our composting process includes a specific Pathogen Reduction Phase. During that time, each windrow is kept at 131 degrees or more for a minimum of 15 days; during that time it is turned at least 5 times. As a result, all the materials in each pile are exposed to temperatures which kill seeds, diseases and insects that may be present.
Our compost is designed to decompose until humification takes place, that is when the compost turns black and soil-like. The high temperature will remain for almost the entire time, cooling off near the end. Mulch, on the other hand, is processed more quickly. We screen it right after it has passed through the Pathogen Reduction Phase, 15-20 days. That keeps the carbon to nitrogen ratio high, which is much desired in a mulch.
MG: So compost is much more decomposed.
WB: Oh much, more. Mulch, by definition, stays above the ground and compost as a soil amendment is incorporated into the ground.
MG: With concerns about water shortages this year, it seems that both products could help quite a bit with water conservation, which will be a high priority this year.
WB: Compost and mulch can make a huge difference by improving soil structure and enhancing water absorption and retention. Between the two, you can trap the moisture in the soil - a big boon as temperatures start to rise in the spring. In contrast, barren soil – dirt with no protective cover - is subject to rapid evaporation, plus wind and water erosion. There is a simple field test to check soil moisture.
Besides that, compost and mulch offer so many benefits. Both improve the soil structure leading to better root penetration and access to the nutrients in the soil which produces more vigorous plants. Maintaining the organic content of the soil is equally important. In undisturbed soils, organic matter builds up quite naturally. But every time soil is tilled, it is aerated. That accelerates the decomposition of organic matter. So any time soil is cultivated, it is important to add organic matter to soil.
Other mulching benefits include weed control, which reduces the need for herbicides (weed killers). Herbicides are yet another oil based product, but they are also water soluble. They contaminate our water supply via rain or irrigation runoff. If we can eliminate the herbicides, we’ll have a cleaner environment.
Compost can also help fight pests in the soil because it is loaded with beneficial fungi that feed on other microorganisms and replace harmful organisms in the soil web. This leads to a reduced use of pesticides (bug killers). Since compost contains nutrients, you can use less fertilizer or none at all. All of this helps reduce our carbon footprint.
Lastly, increasing the organic matter in the soil increases the soil’s capacity to store carbon. It is one of the vehicles that can reverse global warming. Carbon can be stored in the soil for thousands of years. If we can increase the organic matter by 1%, we can remove a tremendous amount of carbon out of the atmosphere.
MG: Whoops ! I didn’t get that last part.
WB: Carbon's place, in the natural cycle of plant growth and decomposition, is quite benign. Plants absorb carbon in the form of carbon dioxide from the atmosphere as part of their normal metabolic cycle, and then carbon becomes a building block of the plant structure. When the plant eventually dies, CO2 is released during decomposition and re-enters the atmosphere. That is a zero-net-carbon cycle; the carbon that was initially absorbed by the plant, is released again. Composting on a Grand Scale
We have increased the amount of carbon in the atmosphere by burning petroleum products. Very simply, oil is old plant material. Over time and under specific conditions, the decomposed plants became oil, which was stored in the earth. When we use petroleum products, that carbon from the ancient plants gets released, and the amount of atmospheric carbon skyrockets.
However, in the compost process some of the carbon is transformed into humus which can have a lifespan of say 1,000 years in the soil. Thus, this becomes carbon in the soil bank, immobilized, taken out of the atmosphere for a long time.
MG: Besides selling soil amendments, what is the biggest contribution your facility makes to Sonoma County residents?
WB: Well, it definitely reduces the cost of garbage. Landfill right now is $93/ton; and yard debris costs around $34.10/ton.
MG: So composting our yard debris, means that less is garbage then is shipped out of the County?
WB: That is right!
MG: What are the biggest challenges you foresee at the facility in the future?
WB: Right now, the biggest challenge for us is economy. If people are stressed economically then buying compost may not be a priority. That will be challenge.
In a normal year, we sell out. We could probably double this facility and sell everything. But the economy is a big unknown. On the other hand, this is a great time for people to grow their own vegetables. What is a more sustainable way to do it than apply ample amounts of compost?
©Sonoma County Master Gardenrs