- What was your PhD research? Tell us about Daisy!
“This really began a long time ago in the search for affordable technologies to digest organic solid waste. These technologies are common in Europe, but they have stringent regulations that restrict alternative technologies, particularly for landfills. This alters the economics because if you can’t take the cheap route, you’re forced to take the expensive route. For this reason, anaerobic digestion is quite common in Europe and relatively rare here, in North America.
About 30 years ago, I licensed a European technology which worked and still works, but no plants could be built in North America because no one would pay the additional costs for processing organic waste – there was nothing compelling them to do so. In Canada, we have some anaerobic digestion, but it’s almost always owned by municipalities who have made the decision to pay the extra from tax revenues to pay for what they consider to be the right thing. The City of Toronto has two anaerobic digesters, they’re both continuous stirred-tank reactors (CSTRs), and they work OK, but they’re very expensive to build and to run.
Myself and a couple of other ‘garbage men’ that I worked with, wrote a report on an existing privately owned digester in Newmarket, Ontario, that had failed and was up for sale. In the report for our clients who had seemed keen to buy it, we said ‘don’t touch this with a 10-foot pole, it can’t be fixed”.You can throw any amount of money at this and you’ll never get it back’. Our clients didn’t buy it, but someone else did and sure enough it failed for a second time. Then we looked at one another and said, ‘If we’re so damned smart, how would we do it?’ And we devised a way to digest solid waste without a lot of front-end pre-treatment – which is costly. And that was the genesis of the research that I did for my PhD.
I first did my masters, my M.Eng., comparing different technologies to the one we had devised and invented, and talking about the regulations in Europe and the ones here in Canada, and came to the conclusion that it could be financially viable. So, my PhD was to evaluate how something like this would actually operate and determine whether it could do the job.
While traditional technologies mechanically convert the waste to pulp and add a lot of water before putting it into a CSTR, our technology puts the solid waste into a cell or vessel without pre-treatment, and circulates the liquids through it. The liquids carry the nutrients and the microbes. If the digester is carefully controlled, you get the same result as a CSTR – in theory.
We actually expected that it would require a much longer solid retention time because mixing isn’t efficient in a circulating system, and so that’s how our reactor , named Daisy, was conceived.
I designed and built what is in [Wallberg room] 343. It took me about a year and a half to design and build it, then came the fearful day that we started it up – just with water running through it. Since, I can monitor it remotely, I would log into the Daisy channel every morning and night to see what was happening.
In fact, it did work, of course there were some problems here and there, but nothing serious. And it proved to be a very durable and efficient way of treating mixed organic waste. We fed Daisy a combination of food waste and various types of paper and cardboard waste. We varied the amount of food waste because in real life the amount of food is variable, depending on the source of the waste The composition of paper and cardboard fibres varies too, but we kept those fixed to be able to complete the experiment in a reasonable amount of time.
From this experiment, I learned four things: (1) Daisy produces no waste water, so although we add water to the waste, the water we add comes out in the digestate at the end, which gets composted in the final step in which water is lost through evaporation, so there aren’t large volumes of waste water that need subsequent treatment, which is an expensive process. (2) Daisy is a very stable system, it didn’t matter how we varied the food waste, we didn’t experience any of the instabilities that people digesting food waste alone experienced. (3) Daisy is as efficient as a CSTR, yielding the same substrate destruction efficiency with the same solids retention time – which astonished me and Professor Elizabeth Edwards. (4) Most interestingly, the addition of food waste enhanced the digestibility of paper and cardboard, and it’s not a small effect. If you add 29% of the COD as food waste and the remaining 71% as paper and cardboard, you can increase the amount of biogas (methane) from the paper and cardboard almost 3-fold, and that had never been identified before. Other s haveco-digested various waste streams, but they hadn’t actually looked at the effect of quantity of food waste on the digestibility of paper and cardboard, and we found this to be a linear relationship.”
- We’ve heard that you’re scaling-up Daisy in Ottawa, what is unique about this technology?
“The next step is a demonstration scale of 4000 tonnes/year – which is quite a scale-up from 5 kg/week! But there is actually no component of this technology that hasn’t been applied before in other ways, at different times, and under other circumstances. So, leaving waste stationary, in an enclosed, sealed, cell is no different from bioreactor landfill technology, where you recirculate the leachate. The recovery of the gas and conversion to beneficial use is no different from landfill gas, which is an established business – I’ve run landfill gas businesses and there’s nothing magic about it. The one step that is a bit of an unknown is the excavation of the digestate at the end, because you have to turn the liquid flow off, drain it and make the digestate aerobic, and hope that odours are killed, before you excavate the digestate and compost it, outdoors, mixing it with yard waste. It will work, but we just have to make sure it doesn’t stink out the neighbourhood!”
- What are some of the challenges of commercializing technology in the waste treatment industry (regulations, value proposition)?
“Regulations are always tough. All through my career, I’ve watched them get progressively more stringent and more onerous and costly to comply with. Some are necessary and others are not. So that’s one challenge. The commercial challenge is keeping costs down. The majority of the revenue in any waste processing operation is from the tipping fee rather than from the sale of whatever wonderful product you create at the end of it. So, in a recycling plant, you sell the paper and the cardboard and plastics that are separated, but they don’t cover your costs. You have to be paid a per-tonne fee to operate the plant, in order to make it economical.
I think that the simplicity of this technology will make it cost-competitive with landfill, but it’s going to be close – it’s not going to be a slam dunk by any means!”
“And the other thing that’s happening, the Ministry in Ontario is in the midst of creating more stringent regulations to keep more and more waste out of landfills, including organics. But until those take shape, and you actually see them in front of you as real regulations, you don’t know if it’s going to happen. But if they do, then it will definitely change the economics of this technology, and any other, but I still think this is the least expensive of any anaerobic digestion technologies around, We just need to prove it!”
- Why is AD bigger in Europe than North America?
“It really began with the Landfill Directive passed by the European Union in 1999. It compels all member states to reduce the amount of organic waste going to landfill to 35% of the organic waste that they landfilled in 1995. This was done progressively over a period of time, and some countries that were more backward than others, took longer to comply… the UK proudly being one of them! But, mostly, the less stringent deadline was aimed at new EU member countries from eastern Europe with terrible environmental track records and legislation. In fact, even in 1999, there were some countries that had already achieved that target, I think Denmark had, Germany had, and a couple of others. The penalties for non-compliance are huge, and every country has to report annually what they’ve accomplished and where they are, and if they aren’t in compliance, they receive huge fines. So that alone created a huge explosion in the development of anaerobic digestion because it’s the best way to achieve the targets, and the Landfill Directive made it affordable.The Europeans are just further ahead!”
- Do think that North America will have the same progression or there will be more of a push for AD?
“It’s happening in a sort of piecemeal way. California has done more, as you would expect. Quebec has done more than Ontario, and BC has done a little more, but there’s no overarching driving force. In the States, the EPA writes regulations for every State in the Union and those regulations don’t require waste diversion to any great extent, so any individual state can put in place more stringent regulations but only within their borders. It’s a patchwork. Even some cities have taken up the cause, but it’s hard to build a business around it. If you’re developing and trying to commercialize a technology, one plant at a time, and carefully selecting places, it’s not easy. So that’s a big challenge. And frankly, the vast land areas we have are pretty good if you want to build a landfill that’s far away from lots of people! I don’t think anything is going to change dramatically the way it did in Europe; it’ll be Province-by-Province, State-by-State, and you’re best not to get too far out ahead of it, or you’ll go broke, and most people have, like the plant in Newmarket!”
- How did working in BioZone help develop this technology?
“Well, enormously is the one word I would use. I didn’t know what I didn’t know when I started. A lot of assumptions that we had made that turned out not to be correct, they might not have been fatal, but certainly knowing now how things actually work, will profoundly alter how the commercial version of this gets built. That accumulation of knowledge is going on today still with the work Teme is doing on Daisy. We’ve asked more questions, and different questions, and the answers to those will also affect how we build it. I’ll give you an example, finding out at the lab-scale that I could get essentially all of the biogas out of this system that it was going to give in 28-30 days, instead of what I thought was going to be many, many, months makes a profound difference to how you design and build it. Now, we won’t replicate Daisy’s performance at full-scale, but we will be able to do in a few weeks or months what we thought it might take as many as 18 months to do. So that alone changes thinking. Also, the yield of biogas is higher, which is a related finding because the two are connected. We’ll get more biogas, in a shorter period of time, with less cost, and we confirmed that Daisy will be stable at a lab scale. We know how maintain that stability, and we know why it remains stable and what will cause it to go wonky.
The other thing was of course the unlimited access to bigger brains than mine! To guide the work, help interpret it and contribute to it in so many ways! I mean, my committee was fabulous, just fabulous. So, lots of ways.”
- BioZone is beginning to develop a Centre for Excellence for Anaerobic Digestion, so will that play a big role in what BioZone can do and further the knowledge that we have?
“We have a lot of know-how, facilities, equipment, and people who have worked in the broadly defined Anaerobic Digestion field. Besides that, we’ve had interest from industry of various sorts in finding somewhere to go to get an objective view of if,and how, AD can help solve their problems, whatever they might be. We are not just interested in solid wastes, but also high volume liquids from processing plants – we’ve been approached by Hiram Walker, Pepsi Co., and others. There is just nowhere for them to go where they can get a trusted, independent, objective view of what they should do. You can’t go to equipment vendors; they’ll just tell you a fairy-tale that promotes their own equipment. And that’s more misleading than helpful. We think there is an opportunity to create a consortium of industries. Maybe two different approaches: one for high-volume liquid streams, and another for solid waste, but there’s bound to be overlap too. But if we can replicate the Pulp & Paper Consortium, for example, we will have a Centre of Excellence for Anaerobic Digestion, and help promote successful adoption. We’ve (gratefully) received money from the Dean’s Strategic Fund to test the idea, and that’s what we’re doing.”
- What does being an Adjunct Professor mean to you?
“It’s unimaginable to me that I would ever find myself in this situation at this age and this time in my life. My parents would have been stunned. This was something that no one, least of all my teachers in school, would ever have predicted.”