Feature: Chemistry Feature: Chemistry
Every day we throw away carbonaceous materials that were originally created from oil or biomass sources at great cost. Montréal-based Enerkem has turned this model on its head. The company uses garbage as a raw material to create chemical building blocks like methanol and ethanol. Currently, in Edmonton, Enerkem is building what will be the world’s biggest waste-to-biofuel conversion plant. Esteban Chornet is professor emeritus of chemical engineering at the Université de Sherbrooke. Ten years ago he co-founded Enerkem with his son Vincent, and he serves as the company’s Chief Technology Officer. ACCN spoke with him to find out more about how Enerkem is making the most of scavenged carbon.
ACCN: Changing garbage into fuel sounds almost utopian. How does it work?
E.C.: Garbage is a very heterogeneous material, so to begin with, it has to be sorted. Recyclables can be recycled, and some waste can be converted by microorganisms, but there is a third fraction which is not possible to either recycle or treat biologically. This ultimate residue has to be shredded to make a product that is homogeneous and fluffy, a bit like confetti. It’s essentially a mixture of about 60 per cent biomass and some 20 per cent plastics; the rest is inert materials, such as glass remnants, sand and some salts. This is the material that we use for gasification.
The material is introduced into a vessel where it is sequentially decomposed and transformed into permanent gases: hydrogen, carbon monoxide, light hydrocarbons such as methane, and CO2. This composition and transformation is conducted in the presence of steam and a small amount of oxygen that provides (by oxidation) the heat for the entire process.
This gas could be converted into electricity, but that’s not our main purpose. Our approach is to use the carbon in this gas as raw material to build molecules that are already used in industry and by consumers, and that normally come from petroleum.
ACCN: Tell us about the new plant you’re building in Edmonton.
E.C.: This is a model of how a project can be developed with municipalities. The city of Edmonton has had a plan for many years to progressively reduce the amount of waste sent to landfill. By the end of the 1990s, they were diverting or recycling about 60 per cent of their waste, but they were not satisfied with that. They decided to commission a third party study in order to find a technology that would use the ultimate residue that is being sent to landfill. It was this group that, in 2002, came across Enerkem. In 2004, the city of Edmonton came to Sherbrooke, and began discussing how we could work with them to use the ultimate residue. The project was primarily driven by the need to increase waste diversion, from 60 to 90 per cent. We began testing for them in the pilot plant, we obtained the data, we looked at the fate of non-carbon components, and they were then satisfied enough to form a partnership.
The partnership is such that they will provide the raw material and we will provide the plant. The city of Edmonton is providing a guaranteed supply of the feedstock, with a small tipping fee, for 25 years. The groundbreaking ceremony took place at the end of August in Edmonton. We are now developing the infrastructure that will host the equipment, which will be coming in after the winter. Eventually, the plant will produce 36-37 million litres of ethanol, but in phase one, we’ll produce methanol only. The phases will be one year apart.
ACCN: Is it true that this is the biggest waste-to-fuels plant in the world?
E.C.: We pride ourselves to say it’s so. I’m a scientist, so you know I’m cautious, but I have looked at the world and I think this is the largest alcohols plant from a negative value waste that has ever been built.
A representation of Enerkem’s waste-to-biofuels facility, currently under
construction in Edmonton, shows the biomass storage building (large
white building, background mid-left), gasifier and gas cleaning modules
(pipes in background, middle),wastewater treatment facility (low, rectangular
building, background mid-right) and methanol and ethanol storage
(large green tanks at right).
ACCN: Gasification has been around for a long time, but your innovation is the use of unconventional feedstocks, like municipal waste. What was the research breakthrough that made this possible?
E.C.: There are three areas that I think constitute the breakthroughs. The first came when we understood that, based on the composition of this material, we do not need to go to extremely high temperatures and pressures. Instead, we could do it sequentially, starting at temperatures that are not very high, perhaps 600 to 700 degrees, and progressively go to 850 to 900 degrees to complete the transformation. The second breakthrough came when we developed a system for feeding this fluffy, low-density material into the gasifier. This seems to be banal, but it’s difficult because you have to feed it in a consistent and uniform manner. Enerkem analyzed the engineering and industrial literature, which led to a few design configurations. Prototypes were built, tested, modified as needed, and re-tested. In parallel, Enerkem connected with suppliers who had had experience in feeding fluffy materials. Their solutions were very similar to the one the Enerkem team had found. The configuration selected is part of the proprietary design package developed by and belonging to Enerkem. This was a mechanical breakthrough.
The third breakthrough, which I think is the most significant, came when we developed a method to remove the contaminants from the gas. That means recovering all the metals and converting all the organic material into useful carbon monoxide and hydrogen. This gas conditioning technology is not necessarily something we invented, but rather we put together by properly assembling a number of steps and unit operations that are known.
ACCN: Clearly these breakthroughs did not happen all at once. Can you give us a sense of how these advances came about?
E.C.: My interest was initially in using wood-type materials. During the 1970s and 1980s, there was a large project in Quebec in which we took forest residues and we began gasifying them. This technology didn’t go far, for a few reasons. Forestry and agricultural waste may be available, but you have to transport them, which can actually be quite costly. They are also rather wet. Finally, the price of petroleum dropped in the 1980s; we had cheap energy and there was no need to develop alternatives. But what we learned during this process was that we could probably apply such technology to more complex feedstocks, if we were able to clean the gas. So, with my team, I took this as a challenge. By the end of the 1990s, we were sure that we could do so, and that is when we put together a company to further develop the technology and eventually commercialize it. The outcome of this was Enerkem, which appeared as a company in 1999, and began operation in 2000.
ACCN: You currently have a demonstration plant operating in Westbury, Que. How does that plant work?
E.C.: We are adjacent to a sawmill which can provide shredded materials from spent telephone poles. The preservatives stay within three inches from the surface, so the poles are sawn, the internal part is sold and we get the shredded material that has preservatives, both organic and inorganic. We convert the organic contaminants into useful gases, and the inorganic ones are neutralized and eventually used for aggregates or brick manufacturing. We also accept municipal solid waste from different places. We have two feeding systems, so we can switch from one feedstock to the other. We also use spent railroad ties, which have creosote in them.
We started the operation in 2009, and we have accumulated a few thousand hours of operation in gasification mode. During this time, the gas was analyzed, and then it was disposed of by flaring. In October 2010, we began using part of the gas to produce methanol. We are very satisfied with the quality of the gas and the methanol we produce. We have planned to do this in three phases: phase one was the gasification, phase two was the methanol, and phase three is the methanol to ethanol, which will begin in this coming year.
ACCN: Are you making money on the Westbury plant?
E.C.: The objective of commercial demonstration plants is to validate the technology at a small commercial scale and to operate on a continuous basis. These demo plants do not represent the economics of the commercial plants and of the company’s business model. Enerkem has the advantage of using a negative cost feedstock for its plants, including its demonstration plant, and has therefore better economics for its demo plant than others.
ACCN: Will you make money from commercial plants, like the one currently under construction in Edmonton?
E.C.: Production at a commercial-scale level is 10 million gallons of ethanol for 100,000 tonnes of dry feedstock. The market price of ethanol today is about $1.80 to $1.90 US per gallon (about $0.50 CAN per litre). We’re able to meet this cost, and have a reasonable return on investment, for the sizes of plants that we are interested in. Enerkem has developed a cost-effective plant model and has many cost advantages. Its commercial plants are expected to deliver good returns.
ACCN: Would this process make economic sense if you had to pay for the feedstock?
E.C.: Yes. Enerkem has other cost advantages, including its standardized manufacturing approach where most of the key process equipment is assembled off-site and in-shop by a third-party contractor under a fixed-price contract.
ACCN: How is the company funded?
E.C.: Initially, it was my family. By 2002, 2003 we obtained our first funding from venture capital. The results were going in the right direction, so in 2005, 2006 we had another infusion of equity capital. You have to do it in funding periods, and we have been successful in attracting interest from both venture capital, and last year from a strategic group,Waste Management Inc. Enerkem is a well-funded company, however, this is insufficient to take all the risks required to move towards commercialization, so we have had support from the provincial government agencies in Quebec and Alberta, from the federal government agencies, both Natural Resources Canada and Sustainable Development Technology Canada, and also lately from U.S. funding agencies like the Department of Energy.
ACCN: What happens to the chemicals that you remove from the gas during the cleaning process?
E.C.: Organics are broken apart into small molecules that are part of our mix for the synthesis. For instance, we transform creosote into carbon monoxide, methane and hydrogen, which are desirable compounds for us.
As for inorganics, we have chlorine, which comes from PVC. It will form hydrogen chloride, and you have to neutralize that by adding lime. We recover it as an innocuous salt, typically calcium chloride. Sulphur is always present, and that can form hydrogen sulphide. We use the same technique; we neutralize the sulphur and produce natural forms of sulphides.
Most metals will stay as innocuous oxides, but you could have some that are volatile either by themselves or as salts. For example, suppose someone has thrown a battery or a thermometer into the garbage. Some mercury will form into gas, because mercury is very volatile. At the end of the gas conditioning system, we have a getter, which is functionalized activated carbon that gets this mercury and transforms it into mercury sulphide. That’s how it is found in nature, and it is innocuous.
A small amount of innocuous solids are produced in our plants. These salts could be used for additives for cement manufacturing, aggregate materials for construction (that is, in concrete or asphalt), or additives for brick manufacturing or landfilling.
Temperatures inside the gasifier (above) at
Enerkem’s demonstration plant in Westbury, Que.
re typically 700° - 800°C. Waste is fed continuously
by a feedscrew (bottom right, yellow).The blue module
on the top left is a cyclone for the gas cleaning process.
ACCN: How does the amount of energy that it takes to gasify the material compare to the amount of energy you get out in the form of ethanol?
E.C.: Let’s say we go all the way to ethanol. The energy efficiency is typically 40 per cent. This is the energy contained in the ethanol produced, divided by the energy in the feedstock, plus any other energy that you add to the system.
We can operate in two ways: we can import electricity, or we can produce our own electricity. In Quebec, electricity is rather cheap, so we have operated using electricity from Hydro-Québec. In Edmonton, we plan to buy the electricity locally as well. We are now at around 35 to 36 per cent efficiency. Eventually, we’re going to put in an engine that will be able to produce electricity and achieve a self-sufficient system. At that time the efficiency will be 40 per cent.
ACCN: The idea of producing fuel from municipal waste is very attractive; why did it take until now to gain traction?
E.C.: I think everything in life has its time. In the fifties and the sixties they asked “why don’t we get some electricity from waste?” So then incineration came, particularly in Europe and Japan. Today, there are a few visionaries, among them Enerkem, that ask “Why don’t we use carbon for a more valuable application than just electricity?” That’s the new paradigm, to capture the carbon in waste and use it as a valuable resource. Our goal is (and I’ll use the Latin word) to valorize carbon. We want to give added value to carbon in waste, and you cannot do that by only heat or electricity production. You have to go into chemical or biochemical production. Soon, people will talk about making garbage into fibres, or into structures, or into fuels. It’s coming, but society wasn’t ready for it until now.
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