(EnergyAsia, February 14 2011, Monday) — The following is an article by Catherine Norwod first published in the February 2011 issue of PROCESS magazine of Australia’s CSIRO science agency.

Efforts to reduce greenhouse gas emissions from iron and steel production have the potential to generate a new industry, producing charcoal for use as a cost-effective alternative to fossil-based coal fuels.

Through CSIRO ’s Minerals Down Under Flagship researchers are developing a new pyrolysis technology that could expand charcoal production in Australia tenfold, and generate a range of valuable by-products.

Principal research scientist Alex Deev says the new technology aims to help the iron and steel industry and other metal extraction industries compete in a carbon-constrained economy.

“The easiest way to reduce greenhouse gas emissions is to replace the fossil carbon with renewable carbon that can be readily absorbed into metal extraction industries, using the same technologies and equipment they have now.”

Charcoal is commonly made via pyrolysis – the thermal decomposition of biomass in oxygen-free or oxygen-poor atmosphere at temperatures above 300°C.

The process has been known for thousands of years. Dr Deev says the challenge today is to develop a pyrolysis process capable of producing large enough quantities of charcoal to make it a cost-effective option.

The new process he is developing may be capable of producing charcoal volumes equivalent to 30% or more of the annual industry coke consumption and will also capture valuable by-products.

Plans have been finalised for a small pilot plant to be built at CSIRO ’s Clayton site in Victoria, to provide proof of concept. The pilot plant will have a charcoal production capacity 250 tonnes of charcoal a year, in continuous operation. If successful, partners will be sought to build a larger prototype, and then to commercialise the process.

Working with BlueScope Steel and OneSteel as industry partners, CSIRO has already identified areas of operations where charcoal might replace coal and coke, if sufficient, low cost, quality supplies were available. For example, charcoal may be able to replace pulverised coal injected into blast furnaces, which constitutes up 25% of the industry’s total fossil carbon consumption. It may also replace at least 50% of the coke fines used for sintering iron ore and the char used to provide the carbon content in steel.

Senior principal research scientist with BlueScope Steel John Mathieson says that if the economics of the new process are favourable, charcoal produced from biomass has the potential to help the industry reduce its net carbon dioxide emissions.

Although some countries use charcoal in steel production, it is not widely used in Australia because of low production and high price, compared with coal and coke. Dr Mathieson says capturing and maximising the value of by-products from charcoal production process will be essential in making charcoal an economically viable alternative to coal and coke in Australia.

The byproducts include bio-oils (also known as ‘wood tar’), biogas and pyroligneous acid (the water-rich condensable phase). The new pyrolysis technique will allow the by-products to be captured and potentially sold into a number of different markets. Condensable pyroligneous acid, also known as ‘wood vinegar’, can be used as a source of chemicals such as methanol, acetic acid and acetone.

Bio-oil and biogas could be used as industrial fuels to produce heat – possibly to dry wood biomass before conversion to charcoal – or to generate electricity into the national power grid. Wood tar is also a valuable source of a variety of chemicals like preservatives, antiseptics, creosote and pitch. However, the technology to fully utilise wood tar as a raw chemical material is still to be developed.

Dr Mathieson says steel manufacturers may be able to use the biogas in the steelmaking production process if charcoal manufacturing is established at steelmaking plants. But charcoal production could also be established as an entirely separate operation, with steelmakers simply buying in whatever product they need.

The new pyrolysis technology CSIRO is patenting is expected to provide a number of benefits over existing techniques, including a lower capital cost to build and operate the plant. Dr Deev says the design of the technology allows it to be scaled for a wide range of reactor units, producing anything from 1000 to 50,000 tonnes of charcoal a year, in continuous operation.

It will be capable of processing cheaper, low-grade woody materials such as forestry residues, wood wastes and wood pellets, while returning a high charcoal yield. The plant itself will draw minimal energy by using the heat generated from the pyrolysis reactions themselves.

The new process also maintains the maximum calorific value and chemical value of the bio-oil and the biogas by-products, and produces only a low level of greenhouse gas emissions.