City of Whitehorse Runs An Excellent Aerated Windrow Composting Process for its Organic Material

The City of Whitehorse operates an excellent organic waste program for their community. They use an aerated windrow composting process, where the material is aerated and turned 8-10 times during the composting process. The screened product undergoes laboratory testing, but also quality testing at their facility before it is sold.  The video below provides a short overview of their program.

The City of Whitehorse is fortunate in that their location and climate does not require that the composting process be inside a building or that they require covers over the windrows. There are a number of reasons why they can produce a quality compost using a simple open aerated windrow infrastructure:

  1. There is not much precipitation in Whitehorse, allowing the composting material to maintain a moisture content of 60% or less. (The risk of objectionable odours during the composting process increases when the moisture content of the composting or curing material increases above 60%).
  2. In addition to the community yardwaste and food waste, the operators add woodchips during the blending process to ensure adequate porosity in the composting material. (The risk of objectionable odours increases when there is not enough air-filled porosity in the composting material to allow oxygen to enter the material).
  3. The windrows are actively aerated to provide oxygen concentrations of 15-18%, which minimizes the production of anaerobic and odorous compounds.
  4. They have the time and space to turn and mix the material adequately during the composting process, usually 4-5 times during active composting, and another 4-5 times during curing.
  5. The composting process is at the landfill, where the small amount of odour, usually mostly from the material being received and before blending, does not have a significant impact on the surrounding community.
  6. The design of the aerated windrows is such that if there was the potential for objectionable odour production early in the composting process, the aerated windrows could be easily covered with a layer of finished compost or wood chips as a biofilter layer to reduce the odour.

The video above demonstrates how the aeration works in these large aerated composting windrows, allowing the City of Whitehorse to compost their organic material effectively with minimal odour during the composting process.

Adequate aeration during active composting minimizes the potential for lingering odour during the curing process, and in the finished compost. In addition, the size of the curing piles are limited to 15 ft high and 30 ft wide and are turned regularly to ensure that the curing material does not become anaerobic.

Before being marketed, the compost is screened to < 1/4″ using a stainless steel trommel screener. The compost is tested for quality parameters at an independant laboratory, and tested at the facility for weed seeds and phytotoxicity.

The City of Whitehorse operates one of the best run composting processes that I have seen with residential organic waste!

Cautionary statement: In areas receiving higher precipitation, both the active composting and curing compost should be covered. The potential odour increases when the moisture content increases above 60%. Its also more difficult to obtain a high quality compost in higher rainfall areas if the process is not covered.

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Composting Food and Vegetable Waste to Minimize Odour and Leachate

One of the challenges with composting food and vegetable wastes is the their high moisture content – they contain 80-90% water. If we want to reduce the risk of odour and leachate during composting, we must reduce the moisture content to about 60%, which requires a lot of bulking agent – 2-4 times the volume of the organic waste! This is particularly a challenge in cases where there is not a lot of wood waste or yard waste available to use as bulking agent!

Our 200 L insulated bin that we call the “magic box” provides insight in how food and vegetable waste can be successfully composted on the small scale, as well as providing insight on the principles of composting that can be applied on the large scale. Given that its been 10 years since we designed the award winning compost facility for Lafleche Environmental in Moose Creek Ontario, there are a number of improvements that can be realized!  (http://www.transformcompostsystems.com/blog/2015/09/26/solid-waste-association-of-north-america-honors-canadian-composting-facility-lafleche-environmental/)

In this 200 L bin, we composted 420 L of vegetable waste having a moisture content of 87%, along with approximately 120 L of yard waste. We accomplished this by grinding the vegetable waste to reduce the volume by 50%, and decreasing the particle size to speed up the decomposition. We then added the vegetable waste over a two week period, to allow the excess moisture to evaporate and maintain moisture contents optimal for composting.

There was minimal odour from the process, and no leachate. Temperatures reached 70 C, and the bin self aerated to maintain optimal oxygen concentration. The resulting compost after the 5 week process was 55%, and contained no odour.

The learning outcomes were that food and vegetable waste can be successfully composted on the small scale with minimal infrastructure, and that the principles of moisture evaporation can be adapted to a larger scale process. The process again verified that when we have optimal aeration rates for food and vegetable waste composting, we must mix the material almost on a weekly basis to prevent preferential air pathways and inconsistent drying!

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New Master Composting Course Offered in Abbotsford

For many of us, composting is a positive word. Unfortunately, for some of us, the word composting brings up negative or conflicting emotion, in part because of the increasing concerns regarding odour, or perhaps because the increasing amount of plastic bits that we are finding in our soils. For others, composting may not bring up much emotion at all, simply because we do not understand it.

In this new course, we will explore and explain the magic of the compost process, and why composting is so important to the health of our planet, and our future in it. Did you know that when we get the composting process right, we can smell it – in parts per trillion? Did you also know that when we don’t get it right, we can also smell it in parts per trillion? We will explore how our nose is so important in understanding the amazing microbial community that lives in our compost – and our soil.

You will have the opportunity to work with our “magic boxes” that help demonstrate and explain some of how physics, chemistry and microbiology work together in the composting process. You will meet Jerome, our new assistant with particular skill in measuring hydrogen sulphide – and to understand how and why this is important! You will learn how two composts that can look the same – can have such as contrasting effect on plants! We will welcome you to the world of worms, their role in composting and in soil.

Interactive learning with the "magic box" and the hydrogen sulphide analyzer

Interactive learning with the “magic box” and the hydrogen sulphide analyzer

This course builds on the Advanced Composting Course that I have taught in Victoria for the last few years. It also builds on the Compost Facility Operator course that I have taught in Abbotsford since 2006 – with more hands on in making and using compost.

This course is for all who are curious about composting and compost use, whether you are a composter, a regulator, a community member, an administrator, media, government staff, or just curious. This course gets us all down in the dirt together, as we explore how important our soil organic matter is, and how it protects us and helps us all to flourish!

We will explore regulation, what it is, what is important, and how we can advocate to make this amazing composting process a socially acceptable endeavor, and how we can ensure that our health and environment remains protected for us and for our children.

The course will be held at the historic Clayburn schoolhouse, a location with a long history of community learning. You will enjoy homemade meals each day, which possibly may include roast beef cooked in the compost pile (or we may just show you how its done). Happy hour is available at the end of the day – we are working towards enjoying it in a hot tub heated by compost!

For more information, http://www.transformcompostsystems.com/learn-compost-courses.php

 

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Does Residential Organics Composting Have to Smell Bad?

A few days before Christmas I sang a variation of “Do You See (Smell) What I See (Smell)” to my wife as we walked through a store parking lot. The smell of residential organic waste composting was distinct! Which of the 350 different chemical compounds that have been measured at compost facilities was it? (e.g. Campbell and Gage).

Its easy to get overwhelmed by the different chemicals that may be in the air coming from compost facilities, with all their different characteristics. There have been some excellent reviews on odour at compost facilities (e.g. CIWMB 2007).  We know that there are mixtures of compounds that give distinct “flavors”. Many conclude that odour is simply subjective, making it difficult to regulate.

Are there indicator compounds that are known to be offensive, and are known to be produced when the composting is not managed well? Yes, there are.

An understanding of the microbes in the compost pile, what they produce and under what conditions they produce them helps us to find these indicator compounds. We’ve known about these specific compounds for almost 100 years, and we’ve known that they are offensive.  Our nose can smell some of these compounds in the parts per trillion concentration.

For mushroom composting, we know that hydrogen sulphide is an excellent indicator compound, and we can measure it at very low concentrations. This is because elemental sulphur is added to the process, and when the process or process water goes anaerobic, teh microbes produce hydrogen sulphide. We don’t have this luxury at compost facilities where commercial and residential organic waste is composted because sulphur concentrations are generally much lower and more variable than at mushroom compost facilities.

The Japanese have been processing organic waste much longer than we have in Canada. They have developed their Offensive Odor Control Law (Government of Japan 2003), which is very specific with some of the odour compounds. We know from research and experience in North America that we are dealing with some of the same offensive odour compounds that include butyric and valeric acids We also know that some of these key odour compounds are produced and emitted when the composting process is not well managed.

Others have learned how to manage these odours from the composting process (eg. Nordic Council 2009). In British Columbia, we can too. We will all have to accept that reducing odor to acceptable concentrations requires a commitment to process, which costs money. We need to work towards socially acceptable organic waste management. Its possible – even with meat waste.

References

CIWMB 2007. California Integrated Waste Management Board. Comprehensive Compost Odor Response Project. San Diego State University.

Campbell, J, and J. Gage. Undated. Characterization of odorous compounds at a composting facility. Columbia Analytical Services http://www.caslab.com/Forms-Downloads/Flyers/COMPOST_BROCHURE.pdf

Government of Japan. 2003. Offensive Odor Control Law in Japan. Office of Odor, Noise and Vibration Environmental Management Bureau Ministry of the Environment Government of Japan. https://www.env.go.jp/en/laws/air/offensive_odor/all.pdf

Nordic Council of Ministers, Nordic Council of Ministers Secretariat 2009. Minimisation of odour from composting of food waste through process optimisation: A Nordic collaboration project. http://norden.diva-portal.org/smash/get/diva2:702178/FULLTEXT01.pdf

 

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Killing Potential Pathogens in Compost – Cold and Calculated

There is hope that smaller communities and institutions who want to compost their own organic waste can do so safely and produce a pathogen free compost. Its been traditionally understood that if we can’t achieve temperatures of > 55 C during composting, we have no hope of killing the potential pathogens and the resulting compost is not safe.

Based on the information reviewed in the last few blogs, as well as our own experience with small scale composting, we are able to produce a pathogen free compost on the small scale. During the review in the last few blogs, we learned that:

  1. pathogen kill during composting is as much about the microbial community as it is about temperature
  2. 40% of compost in small scale composters met the Class A compost requirements – while 60% of large scale composters met requirements for Class A compost

Our own experience with small scale composting confirms that Class A compost can be achieved at lower temperatures. During our compost operator training in November 2016, we created a 100 kg compost recipe that included at least 25% catering waste, 10% poultry litter and yard waste. It was composted for two weeks in an insulated composter, where it achieved 55 C for 2-3 days. We knew that the material on the edges did not meet the requirements for pathogen kill. Following the two weeks of composting, we screened the material to < 1″, placed the material in a garbage bucket outside with a lid, and promptly forgot about it.

As we were preparing for the April compost operator course, we tested the material in the bucket. On November 18, 2016, the compost contained > 2080 MPN/g of both E.coli and fecal coliform. In a second measurement on March 27, 2017, the compost contained < 6.1 MPN/g of both E. coli and fecal coliform.

Was this an anomaly or could this be repeated? We made two batches of compost that included 30-50% food catering waste and the balance yard waste. Again, it was composted for two weeks, screened to < 1″, and placed in covered garbage buckets. This time we thought we would follow it along a bit more closely – and what we found was fascinating! E.coli and fecal coliform counts started high, but actually went higher before dropping and being no longer measureable!

E. coli counts in two small scale batches of compost stored in garbage buckets outside at about 20 C.

E. coli counts in two small scale batches of compost stored in garbage buckets outside at about 20 C.

The data confirm that pathogen free compost can be achieved at cooler temperatures by paying attention to the microbial community.

From our observations so far, it appears that potential pathogen kill was faster at moisture contents of 60% compared to moisture contents of 50%. We are currently testing this theory with another batch of compost that is currently sitting right beside my desk in our office!

We will report on that later as well as on practical implications of VNBC (viable but not culturable) organisms in finished compost.

In the next few blogs, we will focus on the fascinating topic of odour during the composting process.

 

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Helping us Pass the Sniff Test for Composting – the Amazing Actinobacter

The Sniff Test helps us produce great compost with minimal negative effects for our communities. If we get the composting process right, we allow the Actinobacter to flourish. Actinobacter produce geosmin, a compound that we can smell in the parts per trillion which gives the compost a pleasant earthy odour (Gerber and Lechevalier 1965).

“Freshly plowed soil has a typical odor which was undoubtedly detected even by primeval men and extolled in all tongues by bucolic poets” (Gerber and Lechevalier 1965)

The flourishing of Actinobacter during composting has been termed as a sign of composting success (Arnold 2011). Who are the Actinobacter and why should we be amazed by them? Actinobacter are a group of filamentous fungi like bacteria that used to be called Actinomycetes.

“Actinobacter are Gram-positive bacteria that constitute one of the largest bacterial phyla, and they are ubiquitously distributed in both aquatic and terrestrial ecosystems. Many Actinobacteria have a mycelial lifestyle. They have an extensive secondary metabolism and produce about two-thirds of all naturally derived antibiotics in current clinical use, as well as many anticancer, anthelmintic and antifungal compounds. Consequently, these bacteria are of major importance for biotechnology, medicine and agriculture” (Barka et al. 2016.)

Some Actinobacter thrive at thermophilic composting temperatures in the 55-65 C range and are important for decomposition of lignin and celluloses, as well as killing potential pathogens.

“Thermophilic actinobacteria thrive at relatively high temperatures ranging from 40-80 C. These are of two types: strictly thermophilic and moderately thermophilic actinobacteria. The former can grow in the temperature range between 37 and 65 C, but optimum proliferation takes place at 55-60 C. While moderately thermophilic actinobacteria thrive at 28-60 C and require 45-55 C for optimum growth, another group known as thermotolerant actinobacteria can survive at temperatures up to 50 C.” (Shivlata and Satyanarayana 2015).

Many of us, including myself, were aware and taught that Actinobacter were important in the composting process, but they were not very active until later in the active composting sate and during curing (Environment Canada 2013). I stand corrected, and now join others who had already figured out that Actinobacter are very important, even in the primary thermophilic phase of the composting process. I learned by experience in our small scale composter, where the white Actinobacter were obvious even after one week of composting food waste at high temperatures! I also learned that when the composting process is going well, we can smell that earthy smell even after one week.

Actinobacter growth in 50% food waste compost after one week of composting - adequate aeration and temperature management is the key.

Actinobacter growth in 50% food waste compost after one week of composting – adequate aeration and temperature management is the key.

Actinobacter were identified as important primary decomposers during the thermophilic composting of sewage sludge within the first few days of composting (Nakasaki et al. 1985). They observed that the Actinobacter did not grow at temperatures above 70 C.

During composting of municipal organics in Sweden, Actinobacter comprised less than 10% of the microbial population at a full-scale composting plant, whereas earlier observations in a pilot study indicated that Actinobacter constituted 50% of the microbial population during composting (Steger et al. 2007). In further work in Finland, it was noted that the presence of Actinobacter in the thermophilic stage indicated a fast, well-aerated composting process, whereas Clostridium spp (producers of bad odor) indicated an oxygen limiting environment even at high temperature and high pH (Partenan et al. 2010).

We can conclude that there is at least a double benefit to encouraging Actinobacter to flourish at our composting facilities:

  1. Actinobacter produce geosmin, which has a more positive and earthy odour, rather than the disagreeable odours that may of us are familiar with at compost facilities and
  2. Actinobacter produce compounds known to discourage pathogens, not only in the composting process, but also plant pathogens when the compost is used for crops.

Its all about the Sniff Test! With good design of our compost facilities and good management of the composting process, we can do it!

References

Arnold, P. 2011. Actinomycetes: The Sign of Composting Success. Compost Council of Canada. Atlantic Regional Workshop, Halifax , NS. March 15, 2011

Barka, E.A., P. Vatsa, L. Sanchez, N. Gaveau-Vaillant, C. Jacquard, H-P. Klenk, C. Clement, Y. Ouhdouch and G.P. van Wezel. 2016.  Taxonomy, physiology, and natural products of Actinobacteria. Microbiol. Mol. Biol. Rev 80: 1-43 doi:10.1128/MMBR00019-15

Environment Canada. 2013. Technical Document on Municipal Organics Processing. ISBN: 978-1-100-21707-9

Gerber, N.N. and H.A. Lechevalier. 1965. Geosmin, an Earthy-Smelling Substance Isolated from Actinomycetes. Applied Microbiology: 13: 935-938.

Nakasaki, K. M. Sasaki, M. Shoda and H. Kubota. 1985. Effect of temperature on composting of sewage sludge. Applied and Environ. Microbiol: 50: 1526-1530.

Partanen, P. J. Hultman, L. Paulin, P Auvinen and M. Romantschuk. 2010. Bacterial diversity at different stages of the composting process. BMC Microbiology 2010. 10:94 http://www.biomedcentral.com/1471-2180/10/94

Shivlata, L. and T. Satyanarayana. 2015. Thermophilic and alkaliphilic Actinobacteria: biology and potential applications. Frontiers in Microbiology doi:10.3389/fmicb.2015.01014

Steger, K., A.M. Sjogren, A Jarvis, J.K. Jansson and I. Sundh. 2007. Development of compost maturity and Actinobacteria populations during full-scale composting of organic household waste. J. Applied Microbiol: ISSN 1364-5072 doi:10.1111/j.1365-2672.2006.03271.x

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