The task is to write a short paragraph (4-7) sentences in response to the question: What are the major contributors to methane production in Australia?
Use the follow link to access the bibliographical details of each extract and assess the reliability and credibility of each source.(Please, do not use other sources.)
Extract 1 Livestock methane production
Livestock and methane
Some humans (about 50% of us) produce methane when we fart. We all fart, but we don’t all produce methane and it isn’t the methane which smells. Natural gas, which many people use for heating or burn to generate electricity is mainly methane and the Gas company deliberately adds a smell to it, so that it’s easy to detect gas leaks.
Livestock also produce methane, but most of it is burped rather than farted. It is generated by microbes in their guts. Ruminants, like cattle and sheep, have amazing multichambered stomachs called rumens that generate vast amounts of methane during the digestion of their food.
Australia’s Livestock Methane
Australian livestock generate about 3 million tonnes of methane annually. The figure in our annual Greenhouse Inventory is given as 61 million tonnes of CO2-eq (carbon dioxide equivalents). This underestimates the warming impact of the methane by a factor of about 3.
Extract 2 Emission of greenhouse gases in Brisbane (Australia)
Disposal of municipal solid waste (MSW) has been mainly through landfilling, incineration and centralized composting and anaerobic digestion facilities in urban areas around the world. These processes involve direct and indirect emissions of greenhouse gases (GHGs) including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and non-methane hydrocarbons (NMHCs) and contribute to around 3–4% of the anthropogenic GHG emissions in terms of CO2-equivalent (CO2-e) (Pipatti and Savolainen, 1996; Australian Greenhouse Office, 2007; Papageorgiou et al., 2009). More than 70% of MSW is disposed of in landfills in Australian and overseas cities (Ernst, 1990; Aumonier, 1996; Queensland Environmental Protection Agency, 2002; Mohareb et al., 2008). Anaerobic decomposition of these wastes in the landfills results in the emission of CH4 and as such contributes significantly to the global greenhouse budget (Hobson et al., 2005). Disposal of MSW contributed 17 million tonnes CO2-e of GHG emissions in Australia in 2005, equivalent to the emissions from 4 million cars or 2.6% of the national emissions (Australian Greenhouse Office, 2007).
Extract 3 The Australian methane budget
The Government of Australia produces an annual estimate of anthropogenic greenhouse gas emissions (National Greenhouse Gas Inventory, NGGI), including energy (which includes mining related emissions), industrial processes, enteric fermentation from ruminant animals, manure management, rice cultivation, prescribed burning of savannas, field burning of agricultural residues, and landfills and wastewater handling. For 2008, the NGGI reports the release of 5.6 Tg of CH4, or 120 Tg equivalent CO2, equating to 20% of Australia’s total anthropogenic greenhouse gas emissions (Department of Climate Change, 2010). The reported uncertainty on the total inventory (including carbon dioxide and other greenhouse gases) is only 2%, while reported uncertainties associated with individual source categories range from 5% to 50%.
Enteric fermentation from ruminant animals is the largest source of methane in Australia, accounting for 58% of anthropogenic emissions. These emissions are located across the country, with the largest concentration in the more populated regions of New South Wales (NSW), Queensland (QLD), and Victoria (VIC). Energy production, mainly a result of coal mining in NSW and QLD, accounts for 30% of anthropogenic emissions. Landfills and wastewater handling are the next largest source at 12%, and are located near population centers. In the inventories used in this work, methane emissions from Australia are between 9 and 10 Tg/year, of which 5–6 Tg/year are attributed to anthropogenic sources and 4–5 Tg/year are attributed to natural sources.
Methane is produced in wetlands by anaerobic decomposition of organic matter by methanogenic bacteria. The amount of methane produced is highly variable and is most related to temperature and the depth of the water table. Recent work has estimated that wetlands in northern Australia emit on the order of 1 Tg CH4/year and account for 40%–65% of natural emissions, or 10%–20% of all emissions in Australia (Deutscher et al. 2010a). Emissions from oceans surrounding Australia are on the order of 1 Tg CH4 per year (Houweling et al. 1999). Termites produce methane by decomposing organic material via a symbiotic relationship with anaerobic bacteria. Emissions from termites are a significant source of methane in Australia, emitting approximately 1 Tg CH4 per year (Fung et al. 1991). Emissions from termites vary between species, individual mounds within a species, temperature, and moisture (Fraser et al. 1986). Emissions from termites are not well characterized, due to uncertainties in individual termite mound production and location, and issues in scaling up from measurements of individual mounds to the regional and global scales.
Extract 4 Impacts of red meat production on greenhouse gas emissions
The contribution of protein sources to climate change is through their impact on greenhouse gas emissions. The agricultural sector as a whole contributes ~18% of the total greenhouse gas emissions in Australia (Garnaut 2008). Among the protein sources reviewed, the beef cattle and sheep industries contribute 70.1% of the greenhouse gas emissions from agriculture, followed by the dairy industry at 11.6%. The contribution of protein sources to greenhouse gas emissions ranges from the release of carbon into the atmosphere through vegetation clearance, through to methane production by ruminants and management of greenhouse gases such as nitrogen from feedlots. Ruminant animals (cattle, sheep, goats) are the single largest source of Australia’s agricultural greenhouse gas emissions (2861 Gg CO2-e) and alone contribute ~13% of Australia’s total national emissions. In all, 97% of the greenhouse gas emissions are from enteric (digestive-tract) fermentation, with 3% from faeces. Animals such as pigs, chickens and kangaroos have much lower greenhouse gas emissions than ruminant animals (Garnaut 2008).
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