Last week, the Biogas Association held its annual conference in Hamilton, Ontario, which included a full day of touring nearby biogas plants. The purpose of the tour was to continue the up-close and personal learning that has facilitated the growth in the industry we’ve experienced to date. The conference brings together people and companies from around Ontario, across Canada, and increasingly from the US and Europe as well. The tours are the highlight of the conference for me because they provide the opportunity to see different configurations and strategies for effectively and efficiently converting organic waste into energy and fertilizer. These are the biogas plants we toured:
Municipal biogas projects have different priorities and constraints compared to farm-based projects, which are also different compared to commercial projects like ours. These factors drive design decisions. Everyone working in the sector has a different approach to creating as much energy as possible while keeping capital and operating costs low. This includes different ways of processing waste (dry vs. wet), as well as different mixing systems and tank configurations. Each approach has its merits of course, so it brings the plant owner back to assessing what the primary goal of the facility is.
It is also important to remember that biogas plants are living systems, and just as living things tend to get sick if not properly cared for, a biogas plant is no different. This doesn’t just mean keeping the machine well oiled, but maintaining a healthy diet that doesn’t change greatly from day to day or week to week. While the odd piece of cake doesn’t hurt, like us, biogas plants won’t be too productive after gorging on certain foods. Just like us, biogas plants have to watch their intake of junk food–actual junk–like plastic, metal, glass, bones and sand. These materials could break the pumps and mixers that keep the big stomach going, while the bone fragments and sand (collectively known as grit) can settle on the digester floor, slowly reducing the digestion capacity over time.
The biogas tours continue to show me how important it is to design care right into the plant itself. Recipe planning is essential, but also being flexible enough to handle shifts in the recipe. Purchasing sufficient pre-processing equipment to remove as much junk as possible is essential, but having a maintenance plan aimed at minimizing digester downtime is just as important. Without this care and attention to detail, plant performance will suffer, which means more downtime and ultimately reduced profitability.
Just like our bodies, biogas plants work best when the health of their digestive system is at its peak. Should we get sick, a few days off typically resolves the issue. This is where the analogy of a human stomach versus a biogas plant tends to diverge –- a biogas plant cannot take a few days off: Waste management companies and municipalities need somewhere to drop off their waste, because the waste never stops…They would have to deliver it somewhere else–probably less sustainable and more expensive. The biogas plant needs to run with minimal down-time, and to ensure this, it is equipped with multiple redundancies and tested on an ongoing basis, allowing it to be fed 24/7. This satisfies the needs of waste producers, waste haulers and ultimately the people of Ontario consuming the green energy.
All of these lessons have permeated ZooShare’s plans and designs over the years – our focus from the start has been to learn from what is being done around us as the industry grows and evolves. Our biogas plant is essentially a hybrid of the smaller farm-based systems and the larger commercial ones, giving us plenty of examples to draw from to ensure that our gut is healthy and the feeding never needs to stop.
Bonus! Learn what happens to Toronto’s Green Bin Waste
One of the stops on the biogas tour was at Toronto’s Disco Road Green Bin Processing Facility. As many of our members live and work in Toronto, we wanted to share the journey of these organics:
Once the trucks empty the green bin at the curb each week, the waste stream is taken to a transfer station, where all of it is transferred from the smaller trucks making the pick-ups to larger transport trucks. These larger trucks bring the organics to one of two digester projects located within the City, either to Disco Road (near the airport), or the Dufferin Transfer Station (located near Dufferin and the 401).
Upon arrival, the mixture of organics, plastic bags, diapers and everything else that ends up there begins the process by getting tipped onto a big concrete floor in a sealed building.
From here it is loaded onto conveyors by a front-end loader. It is then mixed into large receptacles known as hydro-pulpers, which are used to separate the organic portion from the plastics/metals/other portion. The light and heavy waste products, which collectively make up 19.5% of the total volume entering the facility, are separated here. The remaining mixture is then pumped into centrifuges, which are used to remove the grit (sand, broken glass, broken bones, etc) – collectively totalling another 1.5% of the total volume of material that enters the facility.
All together, Disco Rd receives 300 metric tonnes of material per day. After the contaminants have all been removed, the material is then pumped into the digestion tanks, of which there are 2 with capacity of 5,300 m3 each. Digestion occurs over a period of 17/18 days, at which point the facility is left with biogas and digestate. The liquid digestate is reused in the process, while the solid digestate is loaded onto trucks to be taken to a compost facility north of the City for ‘finishing’. Unfortunately, the biogas is currently being flared (burned to neutralize its impact, but not used for energy), however, there are plans to begin generating power in 2017 that will be used to run the facility and adjacent public works yard. All of this is controlled by a computer system, which is monitored 24/7 both onsite and remotely via cell phones.