The Methane Curse
By Cameron Hunt
29 November, 2006
Znet
According to a November 2004 report by James Hansen of NASA’s Goddard Institute for Space Studies, and Makiko Sato of the Columbia University Earth Institute, Greenhouse gas growth rates: “Given the difficulty of halting near-term CO2 [carbon dioxide] growth, the only practical way to avoid DAI [Dangerous Anthropogenic Interference] with climate may be simultaneous efforts to reverse the growth of some non-CO2 gases while slowing and eventually halting the growth of CO2”. For this reason, they go on to claim that methane, or “CH4 deserves special attention in efforts to stem global warming”.
In another 2004 Goddard Institute report, Methane: A Scientific Journey from Obscurity to Climate Super-Stardom, Gavin Schmidt states that “CH4 concentrations have more than doubled over the last 150 years, and the contribution to the enhanced greenhouse effect is almost half of that due to CO2 increases over the same period”. If you hadn’t been aware of the significance of methane, you were not alone. “Over the last 30 years, methane has gone from being a gas of no importance, to … possibly the most important greenhouse gas both for understanding climate change and as a cost-effective target for future emission reductions”.The obvious question is: If CO2 emissions were responsible for 90% of greenhouse gas (GHG) climate forcing in recent years, and CH4 emissions – the growth of which have recently stabilized – were responsible for only 4% of forcing, why not focus on CO2 emissions? This could certainly be your contention if you disagree, as do I, with the alleged difficulties of halting near-term CO2 growth. But why not address both?
Currently, the majority of the world’s captured methane is flared, as this is less harmful to the atmosphere than simply releasing it. Indeed, CH4 has 23 times the ‘global warming potential’ of CO2. According to the UN’s Intergovernmental Panel of Climate Change Third Assessment Report (TAR), of 2001, “New York City’s 14 sewage plants, for example, generate 0.045 billion cubic metres of methane every year, most of which is flared”. If we multiply this figure out to get an estimate of the total quantity of all methane produced annually by Australian sewage plants, we arrive at 112.5 million cubic metres (Nm3) of methane gas, that must be combusted. Given that this figure excludes amounts of CH4 that are released from other anthropogenic (i.e. human-attributable) sources, such as landfills and agriculture – agriculture alone accounting for over 50% of all anthropogenic CH4 emissions – you can easily imagine that the amounts of energy currently being flared – often at best – is enormous. It should also be clear that methane will make a significant contribution to global warming if we do not capture as much of it as we possibly can, and combust it. Developed countries around the world are starting to wake up to this fact. The 2001 TAR states that “US regulations now require capture of an average of 40% of all landfill methane nationwide”. This will hopefully become a growing international trend, as it is expected that landfill methane gas (LFG) emissions will increase dramatically as the world’s developing nations establish more sanitary, closed (anaerobic) landfills.
Given Hansen and Sato’s conclusion that we need to restrict as many non-CO2 GHG emissions as possible – primarily CH4 – whilst at the same time “slowing and eventually halting the growth of CO2”, why not follow the example set by Linköping, Sweden, over 10 years ago? Since 1994, Linköping Council has operated a biogas train that runs on methane alone; methane produced in its local bioreactor from agricultural waste (the only by-product of which is biofertiliser). Today, Linköping Council also runs over 60 buses, its taxis and its Council cars on methane (biogas); the latter being dual-fuel vehicles that can be easily switched over to petrol, in the same fashion as most Australian LPG vehicles. If we consider the train alone, with a service weight of 47 tons, Australia’s 112.5 million Nm3 of sewage plant CH4 would be enough to drive that train for over 127 million kilometres annually.
Despite being the cleanest-burning fossil fuel, CH4 is still a hydrocarbon, so it too emits CO2 when combusted. The main difference between it and crude-based fuels being that we need to combust methane – unless some mechanism can be found to geosequester all CH4 indefinitely – and are doing this already in those few cases where we have the infrastructure in place to capture it. Also important to note is that when used to fuel light vehicles, for example, those vehicles emit one-third to one-half less CO2 than unleaded petrol. They emit less CO2 than the latest LPG technology, and substantially less than half of the carbon monoxide emitted by either unleaded petrol or 3rd Generation LPG vehicles. So, whilst it is clear that power plants are the world’s biggest CO2 emitters, and that wind, solar, ocean thermal energy conversion and hydroelectric are the obvious ways forward in that sector of energy – the last one more than capable of supplying those baseload needs that we are so often told can only be met by nuclear reactors – readily attainable gains in transport should not be overlooked as part of the overall strategy. Transport is responsible for 14% of Australia's GHG emissions (compared with 35% for coal-fuelled power plants). In the US, cars and light trucks emit more CO2 than either India or Germany, and only slightly less than Japan. They emit nearly as much CO2 as the UK and Canada combined. Of course, were we to one day fuel all the world’s vehicles with CH4 – or ‘natural gas’, as it is often inaccurately referred to (CH4 can make up anywhere between 50 and 90% of natural gas) – this would not mean that we do not still need to work towards greater fuel efficiencies in transport. This will also be required, but the potential benefits of eliminating over one-third of CO2 emissions from light transport, in the very short term, using existing and proven technologies, as well as our current fleet of internal combustion engines and hybrid vehicles, should be clear. If you add to this that those vehicles would be combusting CH4 that we had to combust in any case, and that that naturally occurring methane would displace other crude-based fuels, it becomes a no-brainer.On the topic of fuel efficiencies, it is worth noting that the technology has existed for many years to combust a mixture of approximately 10% LPG and 90% diesel, in contemporary diesel engines (that will no doubt still be in use in 20 years). The benefit of this technology is not burning a lower carbon fuel, as diesel emissions of CO2 are close to that of LPG, but that the presence of the gas results in the typically combusted percentage of diesel fuel going up from 75%, to 85-90%. This results in both an increase in power (and therefore a reduced volume of diesel usage), as well as reduced pollutants. It is unthinkable that liquefied methane – or Liquid Natural Gas (LNG) as it is more commonly referred to – would not have the same effect in diesel engines. This from a fuel we are forced to combust.
Of course, hydrogen fuel cells (HFCs) are already being touted as the panacea for transport energy, but they are not expected to become commercially viable for another 15 years, so we should certainly take steps to reduce CO2 emissions from transport in the meantime. Will our investments on methane infrastructure come to nothing if, and when HFCs come to rule the roads? Certainly not. CH4 is the most common feed fuel used for hydrogen (H2) production today. In any case, there are still some big question marks around H2 production. For example, if the carbon atom split from CH4 in the production of hydrogen is simply released into the atmosphere, then hydrogen is far from ‘emission free’; this then calls for geosequestration. Likewise, CO2 is emitted in the ‘steam reforming’ of CH4, the process that is often used to convert it into hydrogen. We should also consider total CO2 emissions that would be required to produce the necessary HFC infrastructure. For one thing, the tanks required to store H2 must be capable of storing pressures as high as 10,000 psi; a very serious tank indeed. Additionally, how must CO2 must be emitted to produce the actual fuel cells themselves, and how long will these last? Yes, we should continue our research into HFCs, but not to the exclusion of large improvements that can be made today. Conversely, the infrastructure required for LNG is already more or less in place. LPG tanks are capable of holding the pressures demanded of LNG, without modification. The process of combusting that gas in an engine is almost identical. It would also be relatively straightforward for the Government to roll out LNG captured at natural sources – regrettably, at the expense of oil company profits – to existing LPG bowsers. Service stations with more than >1 LPG bowser, for example, could simply have every second or third one converted to LNG as supplies come online. Of course, government regulation would be required to impose LNG bowsers upon service stations, given that the associated petroleum companies would be in no way necessary or useful to the production of LNG, but those stations could be remitted a service fee on any LNG sold.
One of the more obscure outcomes of any large-scale switch to LNG use in transport, might just be that the downtrodden peoples of the Middle East get to witness the final exorcism of the ‘oil curse’, and its associated foreign occupations. I can see them now, at their celebrations, nodding sagely as Australia’s rulers boast to the world of its vast uranium reserves.
Leave A Comment
&
Share Your Insights
Get CC HeadlinesOn your Desk Top