Renewable Gas : Elemental Fuels

It could be said that Climate Change science is an extreme sport – sojourns of several months in Antarctica to drill ancient ice pack, say, or collecting slices of deep sea and lake sediments. Recently, a Chinese team has taken three ice cores from Mount Everest, and a joint European and Japansese expedition have gone pond dipping in the Mariana Trench in the Pacific Ocean to try to better understand the global carbon cycle.

Geophysicists are clearly a hardy bunch, and persistent. Recently there has been a number of breakthroughs into extremely old water, such as a Siberian lake formed by a crater millions of years ago and covered by ice, and water perhaps billions of years old circulating in a Canadian copper mine, an environment that may be older than the development of the earliest lifeforms. A brief article in New Scientist magazine intrigued me – the description of the water which they are studying for signs of microbial activity – “it is packed with hydrogen and methane – chemicals that microbes love to eat […] perfect for life.”

It seems that science has still to uncover the full family of microbes and what they consume and what they produce. Many microbes manufacture hydrogen and methane, and some eat. The migration of microbial life into all parts of the Earth’s crust, including their reach to the bottom of the oceans, was responsible for altering atmospheric chemistry, which enabled the development of oxygen-breathing multicellular lifeforms to evolve. And yet methane and hydrogen have remained vital. These are some of the most energy-packed molecules and some of the most basic. I started to reflect. What struck me was the simplicity and universality of the early chemistry of Earth life, and how these elemental fuels that are good for micro-organisms are also good for humans too.

Methane is the major constitutent of Natural Gas. As one of the most common products of bacterial decomposition of ancient biomass, it is present in deposits of most fossil fuels, including coal seams. Most of this “Natural Methane” in the form of Natural Gas energy fuel produced today comes from fields where it is associated with petroleum oil. Natural Hydrogen is much less common, but research is showing that there could be significant resources in some places. Hydrogen is also a key component in some forms of biogas production – using the decomposing power of microbes to source environmentally clean fuel from harvested plant matter on the surface of the Earth.

Methane and hydrogen are involved in a range of chemistry. Chemical reactions with methane and hydrogen are relatively easy to reverse, because of their molecular simplicity. This makes them highly suited as energy vectors for storage, and the energy they give off when burned in oxygen makes them valuable for human industry, for domestic heating and in the power sector.

Although methane is widely used in energy systems, hydrogen has not been up until now, although there has been talk of a “Hydrogen Economy” eventually supplanting the use of hydrocarbon fuels. This is unlikely to come about in the very near future, although a transition away from fossil fuels is likely to be mediated through the use of Renewable Hydrogen from sustainable, aboveground resources. Why is hydrogen so important ? Because hydrogen chemistry can be used to recycle carbon gas – both carbon dioxide and carbon monoxide, making it a genuine possibility that one day carbon dioxide will be a vital component of energy systems, not a waste gas from combustion.

The most efficient way to use the energy in fossil fuels and biomass is to gasify them for use in combustion, and the common products of this “syngas” or synthesised, synthesis or synthetic gas are hydrogen and carbon monoxide. Convincing hydrogen and carbon-rich gas to become methane packs the chemical energy into a small space and easier and safer to store than hydrogen on its own. Burning methane in oxygen produces carbon dioxide, which, can be coaxed to combine with hydrogen to make more gas fuel.

So there we have it – Renewable Gas : methane, hydrogen, carbon monoxide and carbon dioxide. Using spare Renewable Electricity from our future abundance of solar and wind farms we can make useful gas fuels that can be stored to burn on demand when the air is calm and the sun is not shining. Renewable Gas can cover for the intermittency and variability of other forms of Renewable Energy. To develop Renewable Gas will take some investment, but it will not be an extreme sport like mining ever-more-inaccessible unconventional fossil fuels like shale gas, tar sands and deepwater Natural Gas.

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