This is the short version of my talk. I have a long version too. Even so, I probably have too many slides for the time allotted. So I will try to talk slow. Especially now that there are translaters. If I start talking too fast maybe someone can give me a sign (like Occupy Wall street)
One of the reasons California has the most developed composting sector in the US is a law passed in 1989. It said that every city and county had to recycle half their waste, and also that composting is recycling. In California it is mostly warm, plants grow profusely and in some places yards are big—especially compared to European city yards, so homes generate a lot of yard waste and local officials figured out pretty quick that recycling these types of organic wastes was a smart way to get to that 50% mandate . In 2011 , there were some amendments to the law. That included a GOAL of 75% statewide diversion by 2020 . CalRecycle, where I work, is tasked with achieving this goal. The new law said that businesses and apartments must also recycle. In many places in CA, businesses and apartment dwellers DO recycle, but not everywhere , so this law will ensure that the contributions of the commercial and multi-family sectors to the recycling rate will be going up.
This is a satellite view of a typical California compost facility. Most composting in CA is still relatively low-tech , in giant elongated piles, called windrows . This is a low cost and efficient way to do things, by simply amplifying the processes nature has been using for millenia. Each one of these are probably 2 meters tall, 3 or 4 meters wide, and maybe 50 meters long. Open windrow composting is the dominant type of facility in California . Land is still very cheap in the Western US . So is landfilling. In some places, you can landfill a ton of material for as little as 15 Euro . Also, there is no landfill directive like here in the EU. Organic wastes do NOT have be stabilized before landfilling . So composting facilities compete with landfills for feedstocks. If they raise their tipping fees too much they may lose their raw materials to somebody else who will accept them for less.
Most of the compost is purchased by agriculture. California produces 20 percent of the dairy products in the US (talk more about that later), and more than half of the country's fruits, nuts and vegetable s. California produces around 90% of the grapes in the US, and the wine industry was an early adaptor to compost production and use. So, composting is important to agriculture, but farmers don’t want to pay very much for compost, the average price for finished compost is probably around 10 euro per ton . Nitrogen fertilizer is still pretty cheap. So composting in the US it’s a high-volume business that depends on low-cost production . The problem is that air and water quality compliance is not low cost . Air and water It turns out that paving a 20-hectare pad to protect groundwater would be rather expensive, actually. It turns out that giant pipes full of pressurized air pumps and biofilters are expensive to build and operate. So our infrastructure will have to be modernized but the economics don’t support that . And now we are raising the bar in terms of our recycling goals, but it is becoming very challenging to open new organics facilities and we might even lose a few facilities before the next generation of facilities is ready to come on line..
There is a relatively new type of system that has a good combination of emissions control and costs . Already a few have been built in California, both for greenwaste/foodwaste and also for biosolids composting. There are several vendors of these systems, these photos are from some facilities designed and built by a company called Engineered Compost Systems, or ECS . One of the things ECS does that is a little different is that they have these inflatable sausages that that are inflated under the pile when it is formed. After the piles settles a bit, the sausages are deflated and removed, leaving an air channel which is used to aerate the pile. After a few weeks, the pile can be turned with an ordinary windrow turner , taking advantage of some of the existing machinery. These types of systems are a good bridge from open windrow composting to the modern systems that we need, and they have some water quality and water use advantages over open piles, as well.
Ozone high up in the stratosphere is good, it protects us from harmful radiation. But ozone at ground level is bad for humans, bad for plants, bad for crops. In the US where pollution exceeds national standards, the Clean Air Act requires local air quality management agencies to do everything possible to reduce ozone levels. That also means reduce ozone precursors like VOC s. This year , two California air quality districts enacted regulations to reduce emissions from open compost windrows. These are the first two such regulations in the US. Any new composting facilities in these areas will be built to much higher standards , and will cost a lot more to construct, more than the economics of composting can support in the US. The people who are already composting will be allowed to continue operating for now, but will have to change the way they manage their piles. USCC 2009 Houston Texas A Compost Air Emissions Primer Jan. 27, 2009
So here is the US. California is the third largest state, way out here on the Left coast. Point out SJV, airflow from Bay into SJV, 7 million people living in Bay Area, refineries, port, industry, long commutes. Sierra Nevada mountains, up to 4000 meters, and that this area has some of the highest ozone levels in the USA. SCAQMD, big mountains to its east, over 3000 meters, LA, Sacramento and SF.
The first people to test compost piles for emissions in CA was the air district in the Los Angeles area, known as the AQMD . They have traditionally had the worst air in America and have been leaders many air pollution control techniques. The air in Los Angeles now is much, much better than it was 20 or 40 years ago. These numbers are called emissions factors , and what this means is for every short ton of feedstock, the early studies said we could expect little less than 4 pounds of VOCs. I converted this to mg per kg.. CalRecycle and the AQMD did some testing at this time, trying to see if lasers and traditional measurement techniques using flux chambers, (point to it) this little device here which is barely a half meter across. There was not good correlation between these methods. We also did some work on process controls and found, that a windrow with a lot of woody material gave off less emissions than one with a lot of grassy material. We also found that a turned windrow gave off more emissions than a static pile, but that it also matured faster.
These are RESULTS from CalRecycle’s next study, the most ambitious attempt in the US to quantify the non-methane VOC emissions from open windrow composting, and to test some potential mitigation measures. More than 100 emissions samples were analyzed for this study, probably 5 times more than any of the studies before or since. We came up with a number for straight green waste of about 450 mg per kg, or about one pound of VOC emissions per ton of material. This is just for a windrow process and does not count grinding operations or piles of newly received materials just hanging around. Since this study has been done, there have been other studies done privately , at private facilities, that have found much higher rates of emissions, maybe 20 or 30 times higher. Private sector folks do not publish their data . So I think the truth is, emissions factors are highly variable. Where you set down the little flux chamber really matters, because it is small and the pile is big. Emissions vary hoiur by hour . Put down the flux chamber 5 feet away you could get a very different number . First mention of the pseudo-fiofilter compost cap.
The pseudo-biofilter compost cap is basically a layer of fully composted material on top of a row of freshly ground organic material. This management technique takes advantage of materials on site , such as finished product and oversized materials screened out of finished product, we call them “overs”. Large particles reduce the density of the compost mixture and allow airflow, so when you finally mix the cap into the pile you get a second benefit. You are going to hear about the cap three more times in this presentation. Basically, the microbes living in the finished compost eat up the VOCs migrating up from the actively composting materials; it’s their lunch . In the Modesto study, they ate about three quarters of the emissions over the first two weeks.
In 2009 the San Joaquin Valley Air Pollution Control District contracted for its own study of mitigation measures for open windrow composting. Several methods were tried, and two were deemed to be effective. The first was that irrigating piles within three hours before turning, so that the top of the pile is pretty wet, reduced emissions by 24%. Based on this study, the district created a regulation which requires composters to measure the moisture in the top of the compost pile before turning, and to add water if it is too dry. The irrigation system does not have to look like this, but this certainly is an inexpensive way to do it. The pseudo-biofilter compost cap was proven effective again. These caps were made of unscreened finished compost, they were re-applied every time the pile was turned for the first 3 weeks. So the APCD wrote a regulation that said really big compost facilities had to cover each new windrow with a compost cap, and keep it covered for 3 weeks. These numbers are in short tons, but even with that, 200,000 per year is a very big facility.
The studies that I did with my colleague, Dr. Peter Green at the University of California, Davis, are fundamentally different than all previous studies of composting process VOC emissions. In the past, everyone tried to answer the question, “How much VOCs ?” As I’ve said, it varies… a lot . Dr. Green and I wanted to answer a different question; what kind of VOCs, and even more importantly, do they make ozone ? Because the point of all these air quality regulations is not to protect us from VOCs, though some may be dangerous, but to reduce the build up of ground-level ozone in our cities and the places downwind from them. The assumption has been, if you have VOCs, you make ozone . That’s what Clean Air Act says . Unfortunately, it’s not really true. Not all VOCs are created equal. Some are highly reactive, others are not. A pound of isoprene makes 10 times more ozone than a pound of ethanol. A pound of acetaldehyde makes 10x more ozone than a pound of methanol. Where do compost emissions fit in?
This is the portable ozone formation chamber. It is just small enough to tow behind a pickup truck. Inside the chamber is a 1000-liter teflon bag and banks of lights that mimic the ultraviolet radiation of a typical California summer day. We use a photo-acoustic meter to make real-time ozone measurements in the bag. Later on, we compare these measurements to modeled estimates of ozone formation. The modeled emissions are based on gas samples captured in stainless steel canisters and in sorbent tubes. We take those samples back to a lab and run them through a chromatograph to find out what kinds of gases are in the mix, then that information goes into computer model which predicts how much ozone will be formed. When we compare the two results, they should be fairly close. If they are, then we know we have identified all of the important constituents in the emissions sample. You can see we use a wind tunnel here instead of a flux chamber . This helps reduce the moisture in the sample, which is important for the photo-acoustic measurement. One other thing is added to the 1000-liter teflon bag is a surrogate air that is formulated to match the atmosphere that is found in the San Joaquin Valley on a typical summer day. Because we are not adding composting emissions to a pristine environment, we don’t have one of those. We are adding these emissions to an atmosphere that already has a lot of different stuff in it, and we want to see if we are increasing the amount of ozone that would be formed under those conditions .
We had three rounds of studies , first to get a baseline of different aged piles of greenwaste, we included tipping piles and compost windrows up to 3 weeks old. In our second experiment we test overs , which are the oversized materials screened out of finished compost, not much ozone formation there. We also used overs as a pseudo-biofilter compost cap, and found it reduced observed ozone formation as well as ozone formation predicted by the model. Late last year, a group representing sewage treatment plant operators found out about our efforts, and commissioned our team to study ozone formation from bio-solids co-composting . With pretty much the same results. The bottom line, composting emissions did not form much ozone in the chamber, and the model did not predict that they would. I’m not saying they did not form ANY ozone, but the increase over the surrogate air which mimicked the San Joaquin Valley was very minimal . Compounds like ethanol do form ozone, but they are kind of like the nerdy kids at a school dance. (do they know what nerdy means?) In a diverse atmosphere, there are other compounds which are more attractive (reactive). Every once in a while they get lucky, but most of the time the NOx is going to dance with somebody else.
In California we have this thing called MIR , maximum incremental reactivity. Here in Europe, you have POCP, which stands for Photochemical Ozone Creation Potential . It is basically a measure of relative reactivity; how much more likely is one compound to form ozone versus another. In this slide, we look at how composting compares to other emissions sources , including baselines such as cars and pickup trucks, not heavy duty trucks. We also have the average urban VOC mix here, and two different isomers of pinene, which is a moderately reactive VOC, about 4.5 on a scale that can go up to about 15 . As you can see, the reactivity of composting emissions is quite low, and very close to cow manure . Compost and cow patties are about 1/3 as potent as the typical mix of VOCs found in urban areas . The one agricultural source which is actually fairly potent is silage , the fermented grain and vegetative matter fed to dairy cows. The team from UC Davis tested a lot of different agricultural sources in the San Joaquin Valley, and this was probably the most important revelation. The dairy farmers were not pleased to hear this, but the fact is that the emissions from dairy silage may contribute as much to air pollution in the San Joaquin Valley as automobiles , because there are something on the order of 3 million cows in the Valley, and last I heard, they like to eat every day. The good news is that this should be a win-win situation , because the same management practices which reduce emissions will preserve the value of the food .
The CCORP report grew out of an environment where composting facilities were increasingly being encroached by neighbors in fast-growing communities, and were having trouble with their new neighbors. It was an attempt to bring some science to the issue, and to find out which odor mitigation strategies might work. The best performing mitigation, again, was the pseudo-biofilter compost cap, which worked on the biggest vareity of compounds, whereas some of the commercial applications were only effective against some of the odor compounds. This report runs more than 100 pages and is available for free from the CalRecycle web site.
Based on the literature search performed for the CCORP study, these are some of the potential impacts of variations in the composting parameters and how they might impact emissions, but this is all situational. Some of it is intuitive ; too much nitrogen or not enough carbon in the feedstock and some of it goes up into the air as ammonia or amines. And what the report points out is you need to measure AVAILABLE carbon when calculating a C:N ratio. If you are only measuring total carbon you are overestimating the amount of carbon in your pile, which will likely result in too much nitrogen, and resulting in amine odors, which are not all that pleasant. Similarly, the relationship with temperature is not always straightforward . Certainly, high temperatures indicate healthy microbes and fast decomposition , which is good. Temperature increase up to a certain point does not correlate with more odors, because odorous intermediate products are being broken down. But at very high temperatures , say above 75 C, dimethyl disulfide or DMDS can form rapidly but cannot be degraded biologically. So, my advice if you have odor problems is to download this report for free from our website, and I will have the address in a few seconds.
One more study is underway and funded by CalRecycle . This is part of California’s efforts to assess its greenhouse gas balances as directed under a landmark climate change bill passed in 2006 . Early action measures called for collaborative research on nitrous oxide , which is around 300x more potent than CO2, and closely tied to intensively farmed lands . We are working with a team of researchers to determine what role composting might play in reducing N2O from farming. This is part of a larger effort to establish GHG baselines for a variety of agricultural production systems in California, a very big, multi-year project. Unfortunately, I don’t have any data from this study for you today, and it’s going to be a couple of years until I do, so you’ll have to invite me back in 2014 and I will be happy to report on that!
Every one of the CalRecycle studies I’ve mentioned today is available free on the internet. This is the true beauty of publicly-financed research. So please take advantage of that. The top page is my web page, where there are many links. Go down the line and recap study results.
So, here is the money slide, the summary. If you can remember these points then it was worth it to you, for me to travel across the world. Because it’s going to be worth it for me no matter what! Thank you so much for listening.
If you have any questions… take them now or stop me any time during the conference. Happy to talk to anybody about this subject.
Horowitz shor tversion
VOC emissions from organics management: Measurement, speciation and mitigation Robert Horowitz California Dept. of Resources, Recycling & Recovery (CalRecycle) [email_address]
This Presentation <ul><li>Composting in California today </li></ul><ul><li>Do compost emissions lead to harmful air pollution? </li></ul><ul><li>Composting emissions research </li></ul><ul><li>Odor issues and research </li></ul><ul><li>Climate change research </li></ul>
California Law <ul><ul><li>Cities and counties must divert >50% of their solid waste away from landfills or CalRecycle can issue fines </li></ul></ul><ul><ul><li>Composting IS recycling </li></ul></ul><ul><li>NEW: CA recycling goal: 75% by 2020 </li></ul><ul><li>NEW: Businesses with >3 cubic meters of garbage per week must recycle </li></ul><ul><li>NEW: Apartment buildings with 5 or more units must offer recycling to residents </li></ul>
Open-windrow composting 20 hectare green waste facility near Modesto, CA
Composting in California <ul><li>Most facilities compost source separated green waste in open windrows </li></ul><ul><li>115 facilities / 4 million tonnes processed </li></ul><ul><li>Most compost sold to agriculture, but farmers do not want to pay too much </li></ul><ul><li>New air- and water-quality regulations will require facility upgrades to capture volatile organic compounds and ammonia </li></ul><ul><li>Economics do not support highly engineered, aerated composting facilities </li></ul>
Tarped, aerated systems <ul><li>Micro-pore covers </li></ul><ul><li>80%-plus VOC & NH 3 capture </li></ul><ul><li>Scalable size and cost </li></ul><ul><li>Negative air/Biofilter or positive aeration </li></ul>
Do composting emissions lead to harmful air pollution? <ul><li>Compost piles emit Volatile Organic Compounds (VOCs) </li></ul><ul><li>When reactive VOCs mix with oxides of nitrogen (NOx), in the presence of sunlight, photochemical “smog” results </li></ul><ul><li>Smog includes ground-level ozone </li></ul><ul><li>Ozone very harmful to human health, also damaging to plants and agriculture </li></ul><ul><li>US Clean Air Act regulates ozone levels, mandates action to cut precursors like VOCs </li></ul>
1996-2002 Emissions Studies Southern California—AQMD & CalRecycle <ul><li>First attempts in CA to quantify emissions factors for composting facilities </li></ul><ul><li>CalRecycle helped with concurrent testing using lasers, and studied process controls </li></ul><ul><li>Emissions factors in mg of pollutant per kg of feedstock </li></ul>AQMD data, average of two studies VOC CH4 NH3 Biosolids 1205 8930 1525 Greenwaste 1880 435 410
2005-6 CalRecycle Study Modesto - Northern California <ul><li>70-80% of total VOCs emitted during 1 st two weeks </li></ul><ul><li>70-85% of total VOC emissions vent through top of windrow </li></ul><ul><li>“ Pseudo-biofilter” compost cap reduced VOC emissions up to 75% for first two weeks. </li></ul><ul><li>Additives reduced VOC emissions 42% for first week; 14% for first two weeks </li></ul><ul><li>15% food waste roughly doubled VOC emissions compared to “straight” green waste </li></ul><ul><li>Lifecycle VOC emissions from pure greenwaste windrow @450 mg/kg of feedstock </li></ul>
Pseudo-biofilter compost cap <ul><li>15 cm layer of unscreened finished compost or overs on top of actively composting pile </li></ul><ul><li>Takes advantage of natural pile convection </li></ul>Cap layer Active compost pile Airflow Airflow Warm pile core
2009 San Joaquin APCD study Study: Irrigation system used within 3 hours before turning redu c ed emissions by 24% over first 3 weeks New Rule 4566 : Facilities between 10,000-200,000 tons/year must achieve 24% reduction Study: Pseudo-biofilter compost cap reduced emissions by 53% over first three weeks. New Rule 4566 : Facilities over 200,000 tpy must achieve 53% emissions reduction
2009-2011 Compost Emissions Reactivity Studies <ul><li>Not all VOCs are equal; focus on ozone formation potential (OFP) </li></ul><ul><li>Compare modeled ozone formation to ozone measured in portable chamber </li></ul><ul><li>Tested OFP of windrows, tip piles, “overs” </li></ul><ul><li>Tested impact on OFP of a pseudo-biofilter cap made of composting “overs” </li></ul><ul><li>Chamber method proven at many agricultural sites in San Joaquin Valley </li></ul>
Mobile Ozone Chamber <ul><li>Holds 1000-liter teflon bag </li></ul><ul><li>3-hour experiments </li></ul><ul><li>Used at many ag sites </li></ul>
Results from 3 studies <ul><li>Compost VOC emissions 80-95% low OFP light alcohols: ethanol, methanol, isopropyl alcohol (2 butanol) </li></ul><ul><li>More than 80 other compounds </li></ul><ul><li>Ozone formation potential (POCP): </li></ul><ul><ul><li>Greenwaste composting mix: LOW </li></ul></ul><ul><ul><li>Biosolids co-composting mix: LOW </li></ul></ul><ul><li>Pseudo-biofilter overs cap reduced observed ozone formation by 27-36% </li></ul>
Maximum Incremental Reactivity scale (MIR)* * Similar to POCP
Comprehensive Compost Odor Response Project, 2007 <ul><li>CalRecycle study, available on line </li></ul><ul><li>Literature review on odor impacts of temperature, C:N, moisture, aeration </li></ul><ul><li>Laboratory test of mitigation strategies </li></ul><ul><li>Misting, odor neutralizers, oxygenators, hydrogen peroxide, compost cap </li></ul><ul><li>Pseudo-biofilter compost cap out-performed all commercial preparations </li></ul>
Too hot? DMDS : strong garlic odor Too much woody material (carbon)? Terpenes Too much grass or food (nitrogen)? Amines : smells fishy, putrid or dead Too dense? Mercaptans : smells like rotten cabbage Not enough oxygen? More odors of all kinds Lots of food? Volatile Fatty Acids : smells fecal, sweaty, vinegar
Composting GHG study <ul><li>Funded by CalRecycle </li></ul><ul><li>Research conducted by Univ. Calif. </li></ul><ul><li>Focus on N 2 0 and CH 4 </li></ul><ul><li>Field work 2010-2013 </li></ul><ul><li>Final report May, 2014 </li></ul><ul><li>Concurrent with and complementary to other ongoing ag GHG studies </li></ul>
Related Web Pages <ul><li>My CalRecycle web page: http://www.calrecycle.ca.gov/Organics/Air/default.htm </li></ul><ul><li>CalRecycle Greenwaste Compost Reactivity Study: http://www.calrecycle.ca.gov/Publications/Organics/2011006.pdf </li></ul><ul><li>CASA Biosolids Co-compost Reactivity Study http://casaweb.org/documents/2011/werf2c10_web.pdf </li></ul><ul><li>CalRecycle/Modesto Compost Study http://www.calrecycle.ca.gov/publications/Organics/44207009.pdf </li></ul><ul><li>Composting: Feedstock control vs. Aeration study http://www.calrecycle.ca.gov/Publications/Organics/2008016.pdf </li></ul><ul><li>Comprehensive Composting Odor Response Project http://www.calrecycle.ca.gov/Publications/Organics/44207001.pdf </li></ul>
Summary <ul><li>Composting gives off VOCs </li></ul><ul><li>Emissions rates are highly variable </li></ul><ul><li>MIR / POCP for emissions is LOW </li></ul><ul><li>Composting VOCs around 1/3 as potent as average urban air for ozone formation </li></ul><ul><li>Pseudo-biofilter compost cap effective in reducing emissions and odors </li></ul><ul><li>Greenhouse gas impacts of composting need further research </li></ul>
Thank You Bob Horowitz (916) 341-6523 [email_address] http://www.calrecycle.ca.gov/Organics/Air/default.htm