Ecotricity’s founder, Dale Vince, has been promoting his Gas Mill plan, based on the production of biomethane via anaerobic digestion (AD) of grass, which he says can be a solution to green heating and the UK’s current gas price problems. ‘The answer is not to throw away our national gas grid and the tens of millions of appliances that use it, imposing vast costs on the public - the answer is simply to change the gas we put into the grid. And carry on as normal. Green gas is cheaper, faster and far less wasteful than a switch to heat pumps. And it will work for every home - no exceptions. It will give us a more balanced & diverse outcome in terms of energy supply & form an essential part of the smart grid we need - with gas & electricity grids supporting each other, sharing the energy load of the country.’
The Gas Mill AD idea was first touted by Ecotricity back in 2016, although there was some debate about the scale of its land-use and its overall ecological viability. There were also evidently planning issues with their proposed test plant, but Ecotricity have persevered and a ‘first of a kind’ gas mill, costing £11m, is now being built near Reading in Berkshire. Once fully operational ‘in early 2023’, it’s claimed it will provide all the gas needs of 4000 local homes.
Dale Vince says that ‘traditional methods of making green gas involve use of food waste or energy crops - both have sustainability issues and problems with a lack of scale. Grass is a breakthrough alternative. Ecotricity’s green gas mill will be fed by herbal lays - a mix of grass and herbs, sown and grown on farmland next to the plant. Green gas mills do not require agricultural land and do not compete with food production’.
That’s quite a claim, but Ecotricity has now released a new ‘white paper’ on the UK potential for its Green Gas system, produced by independent academics from Imperial College London Consultants. It says there is enough grassland in Britain not involved in food production to provide gas for all homes and the UK could make all the gas it needs for home and business use if meat production was reduced by 10% and the saved land was used to grow grass. And ‘by 2050 we could be making nearly twice as much gas this way as we currently get from the North Sea.’ It also says that this approach to green gas production can reduce greenhouse gas emissions by nearly 90% when compared to the current use of North Sea gas and synthetic fertilisers- green gas mills produce a natural fertiliser as a by-product. Indeed, Vince says ‘with process improvements it looks possible to achieve an emissions reduction of 99%, compared to North Sea gas and current fertiliser production’.
The cost of producing biomethane from the feedstock is put at £67 per MWh in 2020 and £64 per MWh in 2050. However, the report says that, with development of technology and the addition of enzymes to boost biomethane, costs are expected to fall considerably, with some estimates for new plants to be commissioned this year already suggesting £54 per MWh. That would make it competitive with wind and solar, and of course fossil gas.
Anaerobic Digestion has so far only been developed on a relatively small farm-based scale in the UK, but, although there are some concerns about the ecological/climate impacts of using it as an energy source, the potential of biogas is large, with some recent developments hopefully reducing the impacts- by converting the CO2 produced by AD into more biogas. The Imperial College report describes the AD process as in many ways ‘just like a cow: the grass goes in one end, and gas and fertiliser come out the other. But in this case, rather than the gas ‘escaping’ like it does from cows, it is collected and used to replace natural gas’. It adds that ‘some people use biogas directly in gas boilers for heating or burn it in an engine to generate combined heat and power (CHP). But ‘Green Gas Mills go one step further. Once we have the biogas it is then ‘upgraded’: purified and brought up to the UK’s high environmental and safety standards as biomethane. After being upgraded to biomethane, it can be fed directly into the national gas network to be used for heating in gas heating boilers, cooking on a standard gas hob, or even as vehicle fuel’.
As many others have also noted, green gas does have a lot of attractions and Dale Vince clearly thinks the Green gas mill approach can avoid some of the problems facing the currently favoured electric heat pump approach to home heating. Indeed the Imperial College report highlights significant shortcomings in the government’s national air source heat pump roll-out plan. It claims that such a plan would cost six times as much as a green gas roll out – partly due to the need to triple renewable electricity generation, and there would also be a need to significantly upgrade the grid to deliver it. In addition, the heat pump plan would require the scrapping of millions of gas devices, boilers and cookers, as well as the UK gas grid. The report notes that, currently, it costs £8,000 per home to install a heat pump, which also adds more than 40% to the overall energy bill of each household that uses one instead of gas. The report also flags that heat pumps will not work for 20% of British homes at all – while a further 20% of homes will need significant upgrades. It claims that green gas can be used to simply replace fossil gas in the grid far more efficiently, quickly and cheaply.
All in all, Dale Vince says that the report’s assessment is stunning: ‘A national air source heat pump program will cost six times as much as a green gas program - almost £300 billion versus £50 bn’. So no contest then! But, in terms of deployment, the report’s conclusions are actually more measured. While it asserts that ‘full electrification of domestic heating and delivery via heat pumps makes no sense in environmental, economic or social terms’, it says ‘partial electrification of heating and the intelligent deployment of hybrid heat pump/boilers can deliver better levels of energy security, lower running costs, and greatly reduced infrastructure costs’. So there is a role for green gas alongside heat pumps, with hybrids being ‘the optimal solution in many cases, and at the very least an important interim step on the path to full decarbonisation’. Challenging stuff!
I am not that enthusiastic about Dale’s plans, I’ve been an Ecotricity customer for the best part of ten years but at best I think this is a distraction and that Dale would be much better off investing in renewables. At worst this will likely have a negative impact on local air quality and never really be net zero carbon.
ReplyDeletePersonally, I think the Whit Paper has a few glaring omissions, obviously as Dale has commissioned it, I wouldn’t necessarily expect it to conclude that burning Green Gas is very bad idea. However, there are two reason why I think it is a very bad idea and that Dale’s investment should be switched to investment in renewables.
Local Air Quality
In a very real sense, there is no such thing as ‘green gas’ it’s just marketing, the gas is methane and has caused significant issues with local air quality. Burning methane causes NOx (nitrogen dioxide / NO2) emissions in addition to carbon which have been linked to serious respiratory problems as detailed by the WHO ‘Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2. Reduced lung function growth is also linked to NO2 at concentrations currently measured (or observed) in cities of Europe and North America.’
Net Zero Carbon
Burning methane ‘Green Gas’ creates just as much carbon emissions as burning natural gas, however as the methane is created from the anaerobic digestion of grass it argues that this is net zero carbon. I think the issue of carbon lag is significant and even taking years to be zero carbon is not ideal, but admittedly over time it could be zero carbon. This is however if the methane ‘green gas’ can be converted from grass to combustion without any methane leaks, which I think is practically impossible. The methane leak issue is serious and will prevent green gas from every being net zero carbon, methane is a potent greenhouse gas and even a small percentage of methane leak around 3% will still create significant heating of the atmosphere.
Zero Carbon Electricity
Dale has championed and pioneered zero carbon electricity from renewables and clearly this is more deserving of investment than Green Gas. In terms of electricity the UK Government’s main success story is tuning off all the old coal plants and hence reducing the carbon intensity of UK grid electricity by half in just over ten years. In addition there is the ambition to get a zero carbon electricity grid by 2035 so if zero carbon electricity can be provided for every building surely we should be using this? Direct electricity heating is very expensive to run but heat pumps can help reduce the cost of heating with zero carbon electricity. A lot of building will need a retrofit to add insulation but this isn’t wasted money, it is an investment, more insulation will save them hundreds on their electricity bills.
White Paper
Interestingly only Part 1 of the Whit Paper is written by Imperial Collage London Consultants, Part Two is written by NRS Griffiths about whom I can find no information what so every, smoke and mirrors then, absolutely. This is really two reports presented as one, it would be interesting to ask Dale why Imperial Collage London Consultants didn’t comment on heat pumps given their expertise. I am beginning to think the Dale knows his investment in Green Gas is a bad idea but cognitive dissonance is very strong in all of us.