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Landfill gas (with methane content of 35–55%) adds significantly to global warming if released to the atmosphere. Under the EU Landfill Directive, all landfill sites are obliged to collect this gas if supplied with biodegradable municipal waste. Landfill gas (LFG) can be (i) flared, (ii) combusted to produce electricity, or (iii) upgraded to biomethane. The last scenario is of special interest. In the USA, LFG is now classified as a cellulosic biofuel; in the EU, there is a mandatory target of 10% share of renewables in transport by 2020. A significant challenge for upgrading LFG to biomethane is the high nitrogen content resulting from negative pressure in the landfill. Cost analyses were conducted to compare three technology solutions for LFG upgrading with accessible LFG flow of 250–500 m3/h. If injection to the transmission grid is considered, then a single-step pressure swing adsorption (PSA) system may be viable. The optimal solution suggested is an on-site service station; the cost of this system (including propane addition and service station) was assessed as e0.84/mn3 LFG biomethane. This required a subsidy of e0.55/mn3; this is available in Ireland under the Biofuel Obligation Certificate scheme. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

According to the United States (US) Energy Information Administration (EIA), the annual US natural gas consumption is forecast to grow from 25.6 trillion cubic feet (TCF) in 2012 to 31.6 TCF in 2040 (1 CF≈28.3 L). The main component of natural gas is methane, a potent greenhouse gas (GHG). As the natural gas supply chain grows, there is increased scrutiny over leaks and losses that occur during the multiple stages from development to end users. West Virginia University′s (WVU) Center for Alternative Fuels, Engines, and Emissions conducted leak and loss audits at five natural gas compressor and storage facilities in the Barnett Shale region of Texas. We have reported elsewhere on the site-specific total leak and loss rates.11–13 This article provides an environmental and economic assessment of the total methane (natural gas) losses at these facilities. Other studies report the methane emissions in terms of tons per year, whereas this paper examines the environmental impact of these emissions through an equivalent CO2 emissions rate using multiple global warming potentials. This paper also examines the lost revenue from these leaks and the overall social cost of carbon (SCC) that could be assessed to these facilities under a proposed carbon tax. The methane leaks and losses from these sites result in CO2 equivalent emissions of over 70 000 and 24 000 metric tons annually, using a 20-year and 100-year global warming potentials (GWPs), respectively. Using a SCC of $ 37 per metric ton, this would result in annual costs of $ 2.6 million and $ 915 000 for these sites based on the respective GWPs.

In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas, concluding that the climate impact of shale gas may be worse than that of other fossil fuels such as coal and oil because of methane emissions. We noted the poor quality of publicly available data to support our analysis and called for further research. Our paper spurred a large increase in research and analysis, including several new studies that have better measured methane emissions from natural gas systems. Here, I review this new research in the context of our 2011 paper and the fifth assessment from the Intergovernmental Panel on Climate Change released in 2013. The best data available now indicate that our estimates of methane emission from both shale gas and conventional natural gas were relatively robust. Using these new, best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years.

Power generation in Australia is responsible for about 25% of the country's greenhouse gas emissions. Due to the abundance of coal, most power stations use this fuel as the primary source of energy. The high carbon content of coal combined with the relatively poor power generation efficiency of these facilities, explain the contributions which power generation make to Australia's greenhouse gas emissions. In this paper, the effects of these two parameters, ie, fuel type and generation efficiency, on greenhouse gas abatement is studied. It is shown that by controlling these two factors, there is a significant potential to reduce greenhouse gas emissions in Australia. An analysis of the electricity market showed that renewable energy projects and natural gas fired power stations cannot compete on price with coal fired power stations. Carbon taxes and green energy programs are seen as the most likely ways to make renewable energy and natural gas competitive with coal, and thus reduce greenhouse gas emissions caused by power generation.

Municipal Solid Waste (MSW) landfills world-wide are experiencing the consequences of conventional landfilling techniques, whereby anaerobic conditions are created within the landfill waste. Under anaerobic conditions, slow stabilisation of the waste mass occurs, producing methane, (an explosive, 'greenhouse' gas) and toxic leachate over long periods of time. As a potential solution, it was demonstrated that the aerobic degradation of MSW within a landfill can significantly increase the rate of waste decomposition and settlement, decrease the production of methane gas, reduce the level of toxic organics in the leachate and decrease quantities of landfill leachate that need treatment. This paper summarises the successful results of two separate aerobic landfill projects located in Georgia (USA) and discusses the potential economic and environmental impacts to world-wide solid waste management.

Landfills are considered to be an important global source of the greenhouse gas methane. These emissions are especially caused by inadequate gas collection systems, uncontrolled emissions from old dumps and unauthorized open dumping. The subsequent capturing and disposal of landfill gas from old landfills is technically difficult and very costly. A low-cost alternative to the conventional methods is the microbial oxidation of methane. For this purpose it is necessary to spread cover layers much in the same way as is done for large biofilters. This calls for sufficient knowledge about the biology of the methane oxidising microorganisms and the resulting requirements to be met by the substrate. Laboratory studies have proved municipal solid waste compost and sewage sludge compost to be suitable carrier substrates.

About 240 x 106 tonnes of industrial waste, 104 x 106 tonnes of municipal waste and more than 60 x 106 tonnes of sediment sludge are landfilled (65 per cent), incinerated (24 per cent) and partly recycled in Europe annually. About 60000-120000 landfill sites, occupying 800-1700 km2, are recorded in the EEC, of which a limited number are in operation. These sites generate 12.5 x 109 m3 of landfill gas annually, of which about 755 x 106 m3 are presently recovered, and 0-1-4-0 x 106 m3 of heavily polluted leachate, which is dispersed to ground and surface waters. the area with polluted groundwater increases annually by 1-10 per cent (1200-12000 km2 of contaminated land). Landfill gas contains carcinogenic and pathogenic components and contributes 2 per cent of the total emission of greenhouse gases; locally it is a potential hazard. Incinerators reduce the solid volume to about 30 per cent of the original but cause the atmospheric deposition of acids and dioxins. Emissions of landfill gas, leachate and atmospheric deposition have been recognized as potential chemical time bombs (CTBs). Models are currently available for the estimation of the time at which the effects of these CTBs will become manifest. It is recommended that an inventory of all landfills should be made to assess the potential hazards in detail, to encourage institutions to initiate the clean-up of contaminated sites and the aftercare of closed sites, and to set up a co-operative network within the EEC.