The Oil Drum: Australia/New Zealand

Powering transport using liquid petroleum gas, compressed natural gas or fuel produced by gas-to-liquids processes are options that have received varying amounts of attention in recent years as the oil price climbs ever higher. While shifting dependence from one fossil fuel to another doesn't make a great deal of sense when you take peak oil and gas into account, there is a renewable option for producing gas - biogas.

One recent example of biogas use in Australia is a pilot project by horticulture company Growcom to convert banana waste into biomethane, which will then be used as fuel by cars converted to use compressed natural gas and by a generator for electricity production.

The processing plant uses an anaerobic digester - in trials, the banana waste produced maximum yields of 398 litres of methane per kg of dry banana. With this yield, 1 ton of bananas per day can generate around 7.5 kW of electricity - enough to supply six to eight modern households.

The authors of this study are: Rainer Zah, Empa; Heinz Böni, Empa; Marcel Gauch, Empa; Roland Hischier, Empa; Martin Lehmann, Empa; Patrick Wäger, Empa

Empa, Swiss Federal Institute for Materials Science and Technology, Technology and Society Lab, Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland, www.empa.ch/tsl

Executive Summary

In connection with the worsening scarcity of fossil fuels and climate change the idea of using renewable energy is attracting interest both in the Swiss public eye and in industry. Fuels made from biomass - so-called biofuels - are currently the most important form of renewable energy in road transportation and could at least over the short to medium term take on a role in reducing greenhouse gases and our dependency on fossil fuels.

In Switzerland therefore important political decisions have to be made against a background of giving a tax break for renewable fuels as opposed to diesel and petrol.

Although biofuels from renewable resources exist, a wider range of environmental impacts may result from their cultivation and processing than those from fossil fuels. These range from excessive fertilizer use and acidification of soil to a loss of biodiversity caused by clear cutting rainforest. Besides that, one should not forget that expanding agricultural energy production may lead to land use conflicts with other land uses such as food production or the conservation of natural areas. Therefore energetic efficiency and the attainable reduction in greenhouse gases should not be taken as the sole criteria for a holistic environmental evaluation of these alternative fuels.

The objective of this study is to evaluate the environmental impacts in the whole life cycle of biofuels used in Switzerland. Firstly an action-oriented analysis of the environmental impacts of renewable energy carriers was to be developed. Secondly the objective was to draw up a "comprehensive environmental analysis" of the various biofuels, which could serve as a basis for enforcing the exemption of renewable fuels from the excise duty on diesel and petrol. In addition, the effects of using the fuel were to be compared with other ways to use bioenergy, such as heat and power generation.

Editorial note: there is a comprehensive glossary at the end of the piece, as are the references denoted [X] throughout.

Anaerobic Digester

The Ontario government has recently been emphasizing its green credentials, particularly in relation to small-scale renewable generation, in the run up to a provincial election this fall. The Standard Offer Program (SOP - previously discussed here) is claimed to provide a framework for bringing a substantial array of new embedded generation on to the grid - generation based on different energy sources and varying widely in size. This is exactly what needs to happen if Ontario is to avoid a painful energy squeeze in the future, due in part to the approaching decline of natural gas supplies in North America. However, achieving it is proving to be far more difficult than one might reasonably expect.