Syngas and Char

I found a paper by The Australian Academy of Technological Sciences and Engineering on Biofuels in Australia. In it they classify biofuels into generation 1 and Gen 2 fuels. They are more categorisd by the processes used to make the Fuels and their source materials. Basicly if you using the sugars or the oil produced by food crops to produce fuel these are the Gen 1 Biofuels. Gen 2 Biofuels come from low value, Plentiful and currently mostly unutilised sources like Cellulose.

Generation Resources Status
1 Sugarcane and cereal crops Mature worldwide
2 Bioethanol – lignocellulosic wastes; Early stage worldwide
Biodiesel – algaes, FT
Synthetic diesel, methanol and DME
3 Biorefineries Still in conceptual stages


They also talk about, what in Australia is called Biochar.

Pyrolysis has been used for centuries. Wood and other carbon products, including sewage, are heated in the absence of oxygen to 475°C to 500°C. Applying ‘slow pyrolysis’ about one third of the feedstock weight is released as water (or steam), one third converts to char and one third to a fuel gas which can be further processed to a liquid fuel using, for example, the Fischer-Tropsch process, or burned to generate electricity.

Lehmann, Gaunt & Rondon (2006) report that minor process modifications can alter product compositions and can convert between 40 and 50 per cent of feedstock carbon conversion to char. Although char can itself then be burned for heating, as outlined by Marris (2006), Amazonian Indians for thousands of years have known that char burial leads to substantial crop improvement. Recent testing by the NSW Department of Primary Industries shows that as well as improving yields up to 200 per cent, char also reduces agricultural nitrous oxide emissions, possibly more so than achieved by replacing mineral oils with biofuels. This benefit adds to more obvious GHG reduction by carbon sequestration, e.g. burying carbon. Amazonian soil tests show that carbon remains in the soil for centuries, making it more effective than tree sequestration and competitive with geosequestration on a long time scale.

Over 1100°C gasification occurs. In combination with the Fischer-Tropsch process it is thus possible to produce diesel fuel from coal (Worldwatch Institute 2007). Currently this combination at large scale is uneconomic for biomass. Gas cleaning of tars and fine particles is problematic. Stucley et al. (2004) illustrates differing sized gasification plants costs. He notes that if sited close to gas use, and with carbon tax and dry land salinity reduction payments introduced, the process may be economic depending on the size of the subsidies. Small biomass plants, suitable for large towns, are also economic without subsidy whereas scale economies require coal-fired power stations to be far larger. At still higher temperatures (5500°C or more) plasma is formed56 and virtually the entire resource transformed into fuel gas. An advantage is that any bacteria or viral contamination (e.g. sewage or hospital waste) is rendered inactive. Small scale prototypes have proven cost-competitive with conventional fuels operating at this temperature.

‘Fast’ or ‘flash’ pyrolysis has been under active development for the past 25 years. In this process up to 75 per cent of the biomass may be transformed into a liquid, having approximately 60 per cent the energy content of petroleum diesel on a volume-for-volume basis. This bio-oil can be used in various applications, such as for food flavouring but needs to be upgraded for use as a transport biofuel because of its high phenol content. It has been trialled for stationary energy applications and is being researched internationally as a transportation fuel. The Canadian company Dynamotive has built commercial plants up to 200 tonnes per day of biomass and has successfully run a 2.5 MW combustion turbine on this fuel.

They then go on to talk about Syngas. Saying that it is more energy efficient to use the gas in a similar way to LPG.

Biomass (trees, weeds, shrubs, or almost any other carbon source including sewage) can be converted efficiently into fuel gas (syngas) comprising hydrogen, methane (natural gas) and carbon monoxide using elevated temperature (>700°C) chemical processes. This distinguishes it from biological processes such as anaerobic digestion which produces biogas. Syngas can be used in standard internal combustion engines with only minor modifications and much more efficiently than direct combustion of the original fuel. Although syngas can be further converted into a liquid fuel using the Fischer-Tropsch process, it is more energy efficient to compress it for vehicle use, as with LPG and CNG. Technology already exists for operating large trucks on a combination of gas and liquid fuels or even entirely on LPG. Gas fuels have less adverse effect on air quality because they burn more cleanly than liquid fuels with lower toxic emissions (Beer et al. 2001) and less impact on human health.

Check it out is a good report.

Cheers L.