Waste to Renewable Chemicals

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The Process

The Enerkem Alberta Biofuels facility uses a proprietary thermochemical process, but before the waste even gets to the biofuels facility, it goes through the city’s separation process.

Trucks drop loads of garbage onto a tipping floor. From there it is separated in a series of manual and automated processes. The compostable material is separated from non-compostable, which becomes the “refuse-derived fuel” for biorefinery. This term refers to materials like soiled wood, paper, fabrics and basically anything else carbon-based that cannot be recycled are chopped up and turned into a kind of garbage fluff.

This refuse-derived fuel is what goes to the Enerkem biofuels facility where, in a four-stage process, it is turned into syngas.

One of the major characteristics that differentiates this process from other waste to fuel processes is that any waste that contains carbon is considered feedstock. That includes waste, woody biomass, treated wood, construction or demolition debris—even plastic. According to David Lynch, general manager of research and development at Enerkem, “As long as it has carbon and you can run it through the feed system and get it into the gasifier, you can run it.”

The system is most efficient when moisture is less than 20% and there is a certain minimum amount of carbon in the mixture. To ensure there is always the right blend of raw material, a feedstock storage facility is located at the refinery. It has seven bays containing various types of feedstock such as construction and demolition waste, plastic bags and packaging that couldn’t be recycled, and some household waste.

In the second stage, the fuel is conveyed directly into the gasifier, which is a high-temperature, low-oxygen chamber where the energy within the fluff itself is used. There the hydrocarbons in the fluff are cracked to make the syngas. Steam and some oxygen are added to bring the temperatures to optimum efficiency. According to Lynch, whether it’s plastic or wood or another hydrocarbon fuel, the system breaks it down to a consistent syngas.

“We use a SCADA system,” said Lynch. “Everything is controlled and automated with a PLC. Most of the valve operations are automated. We use all kinds of actuators and valves of all types. Solenoids to control the regulators, pressure-relief valves, check valves, quarter-turn ball, pressure control, gate valves and basically every other kind of valve used in any normal refinery.”

“We also cover the gamut of materials for our valves,” said Lynch. “We select the materials specifically for the application within the system. Some are more resistant to abrasion, some more resistant to the water process.”

In the third stage, the syngas goes through a robust gas conditioning system that will remove any kind of particulates or other gases before the final step in the process.

The catalytic portion is the fourth stage of the process. Enerkem uses traditional catalytics to convert the syngas into chemical intermediates, and the first in Enerkem’s modular process is methanol catalyst “If you want to make methanol,” said Lynch, “That’s all you really have to do. The end result is standard chemical-grade methanol.” Lynch said the company is taking a phased approached to production, so a module converting the biomethanol into advanced ethanol will be added by the end of 2015.

More Modules

“Actually, the majority of construction of this plant was modular,” said Lynch. “It was built mostly off-site and shipped to the site in modules. Now when the new module is brought in, we can just hook it up to build the overall system. This maximizes our options in any one locale.”

As an aside, Lynch noted that the company is looking at similar processes to build modular units that can then be shipped to remote communities so that they can use local available biomass and/or waste to produce power and reduce landfills.

The whole system is powered through municipal utilities at this time, but Lynch said that they are looking eventually at considering power generated from the landfill and anaerobic digestion. “But this process doesn’t use that much electricity,” said Lynch. “There’s some to compress the gas and to run the pumps, and we are using heat integration within the process to reduce energy costs, but it is not energy intensive.”

When asked if there were any challenges that valve manufacturers could help Enerkem address, Lynch said, “Valve performance is a critical aspect of this process. We had some challenges earlier on, when we built the pilot plant in Quebec in 2001 and then later the demo plant. But we found good suppliers that really know their business, and we were able to find the products that hold up to the duty cycles in this plant. We’re really pleased with that.”