A February report in the Charleston Regional Business Journal describes efforts by Agri-Tech Producers CEO Joe James to develop four torrefaction plants in South Carolina over the next five years. Integro Earthfuels also has big plans for torrefied biomass. They’ve announced intentions to build 10 commercial-scale torrefaction plants in the United States, the first of which will be located in Roxboro, N.C. and have an initial capacity of 84,000 tons per year.
We think this trend will continue. Why? While producing energy from biomass has many benefits — it is a local, renewable and carbon neutral energy source — there are also some obstacles: moisture content, energy density and transportation costs and logistics. These problems can all be solved by a process that uses torrefaction and pelletization (TOP) to create torrefied biomass, also known as e-coal and bio-coal. The torrefaction process is similar to the method used to dry and roast coffee beans: you apply heat (400-570 °F) in the absence of oxygen, thereby removing moisture (the origin of the word torrefaction are French, meaning “to make thirsty”). The benefits of torrefied biomass include :
- It takes up less space and is cheaper to transport; as a result, it can be shipped longer distances making exporting biomass a more realistic and profitable venture. One study in the Netherlands found that long-distance trade and logistics of torrefied biomass were 30-70 percent more economical than raw biomass.
- Unlike regular pellets, which reabsorb water during shipping and storage, torrefied biomass resists water. Like coal, it can be stored without cover.
- It is extremely stable; it can withstand 1.5-2 times the crushing force than regular pellets.
- The decomposition that occurs at this temperature level cause the fibrous structure of the wood to loosen; as a result, its grindability improves to the extent that it can be co-fired with coal at the amounts of 10, perhaps even 30 percent. Because it can be pulverized with existing coal pulverizers, the capital costs necessary for co-firing are reduced. This same characteristic makes bio-coal an ideal feedstock for converting biomass to cellulosic ethanol, since it makes gasification easier.
- Torrefaction produces consistent and uniform feedstock; these qualities reduce risk of damage and inefficiency in wood-to-energy processes.
- Most of the volatile organic compounds, like pinene and turpene, are burned off during torrefaction; as a result, less smoke is produced when the e-coal is burned and there is less danger of slagging a boiler.
- The thermal efficiency of the torrefaction process is 96 percent. The treated biomass has a heating value of 11,000 Btu/lb, which is similar to that of coal at 12,000 Btu/lb.
At this stage of development, it appears that torrefied biomass has great potential for reducing the costs of the biomass-to-energy production chain. Two markets have the potential of spurring the development of torrefaction plants. As utility companies are being required to reduce carbon emissions by state renewable energy standards, more of them are investigating co-firing wood with coal. Their costs may be reduced significantly by using torrefied biomass. Because torrefaction makes wood more portable and durable, European energy companies will likely prefer bio-coal to regular pellets; this could lead to a real boon in exports.
Bergman, Patrick and Jacob Kiel. "Torrefaction for biomass upgrading," Energy Research Centre of the Netherlands. Available at: www.ecn.nl/biomass
Biopact. "Integro Earthfuels plans first torrefaction plant in the U.S." Available at: bestwaytoinvest.com/
Biopact. "Torrefaction gives biomass a 20% boost, makes logistics far more efficient." July 25, 2008.
Hadaway, Chelsea. "Biomass at forefront of dean energy in S.C." Charleston Regional Business Journal February 16, 2009. Available at www.charlestonbusiness.com
Hopkins, Chris and Joe James. "Using Torrefied Wood for Electricity and Pellet Production." Presentation. February 2008.
Zanzi, Rolando, et al. "Biomass torrefaction." Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.