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COLUMN: Composting must meet several competing objectives

by Colin Isaacs
EcoLog, 10/4/2019 2:42:00 PM

The 29th annual conference of the Compost Council of Canada, held in Guelph, Ontario in September 2019, highlighted some of the changes and challenges facing all who are involved in some aspect of the composting industry. This includes not only composting operators but also generators of end-of-life organic materials, farmers as generators, the food industry, waste haulers and processors, equipment suppliers, compost distributors, and farmers, landscapers and gardeners as receivers of finished compost. 

The good news is that the mood of the Canadian composting industry seems to be on an uptick. Challenges, and there are many, appear to stem from uncertainty as to what the industry is supposed to be about. 

Traditionally, composting has been viewed as a way of diverting organic waste from landfill. Food waste comprises close to 40% of the total Canadian waste stream. When yard waste, grass, leaves and woody material are added, then organics can be 50% or more of the total waste stream. Many municipalities have already achieved diversion of most of yard waste to compost, either through industrial facilities or through backyard composters, but better management of food waste is still a learning experience in many towns and smaller cities. 

A key topic of many of the conference presentations, though sometimes expressed less than explicitly, was whether the objective is to maximize the diversion of material from landfill, to maximize the quality of the finished compost even if this means diverting some of the organics to landfill, or to produce the maximum quantity of energy in the form of renewable natural gas from anaerobic digestion. Anaerobic digestion is not technically composting but the term is often used to include all forms of processing of end-of-life organic materials. 

Unfortunately, it appears that these several objectives are not always compatible. High-quality compost requires taking the best of the yard and food waste, screening out anything that will not compost, and sending the screenings to landfill. Anaerobic digestion facilities require a similar high-grade input stream but may be even more sensitive to contamination, as their systems are more complex. 

Maximizing diversion from landfill means accepting as much compostable material as possible, though this may include materials which compost more slowly, increasing the processing time as well as the amount of screening required, and, hence, the total cost of processing. 

The theme of the 2019 Compost Council conference was Recycle your Organics — Return Life to our Soils. While increasing the organic content of our soils has always been an objective of composting, it was the focus of the 2019 agenda. 

Professor David Johnson of New Mexico State University emphasized in his keynote address the importance of getting the right mix of fungi and bacteria in agricultural soils. His data showed that yields of food can be substantially increased if this is done correctly. Soil is not just a medium to hold the plants but is vital for feeding the plants, and yields will be much less than optimal if the balance of microorganisms is sub-optimal. Several other speakers, including Professor Ralph Martin of the University of Guelph, echoed this message. 

Manufacturers and brand owners of compostable products held a one-day event before the Compost Council conference to discuss some of the challenges facing the compostable plastics sector. Composters and compostable product advocates have been somewhat at loggerheads for several years, but the gap appears to be closing. There appears to be agreement that compostable products and packaging can be appropriate in applications where the plastic is contaminated with food waste and where a lifecycle study shows that the compostable product or packaging has in practice a lighter environmental footprint than other alternatives. 

Some, perhaps many, people in the composting industry appear to have recognized that compostable plastics can be composted but that the technology currently being used for composting in Canada may not have been designed to accept the new materials. 

Hence, what may be the most challenging question of all, the elephant in the room at the 2019 Compost Council conference: Who will pay to build and operate a network of composting facilities in Canada that can maximize diversion of waste, help restore our soils to the microbial balance required for maximum productivity, and assist in meeting our energy needs through maximizing production of renewable natural gas?  

Colin Isaacs is a consultant in Sustainable Development for Business. His company organized the Second Canadian Summit on Compostable Products and Packaging that was held in advance of the Compost Council of Canada conference.

Colin Isaacs is a scientist and analyst with CIAL Group who focuses on sustainable development for business. He was selected by Environment Canada to be the principal author of the waste management chapter in the report The State of Canada’s Environment 1991. Colin can be reached at (416) 410-0432 (phone), (416) 362-5231 (fax), and colin@cialgroup.com (e-mail).

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