The days of giving natural gas a free pass as a “bridge fuel” toward a low-carbon world are over.
Years ago, replacing coal and oil with natural gas seemed the lesser of evils, because at the point of combustion gas releases less carbon dioxide than other fossil fuels. But the equation has changed: the cost of power generation from wind and solar has dropped and energy storage technologies have evolved, allowing renewables to compete head-to-head with fossil fuels.
In short, we can skip the baby steps and transition straight to renewable energy sources.
Good thing, because to keep global heating under 1.5°C relative to pre-industrial temperatures, gas use must decline 43% by 2050, according to another recent report by industry watchdog group Global Energy Monitor.
“The fear is, if we invest in biomethane infrastructure for applications that are ultimately going to be electrified, there could be stranded assets and investments that don’t prove their worth over the test of time.”
This isn’t slowing down the natural gas industry. A US$1.3 trillion push is on to develop LNG to an integrated global market, says the report, and a third of that capital expenditure could be in Canada.
In BC, that means more fracking and more methane – the primary component of natural gas and a greenhouse gas 86 times more potent than CO2 over a 20 year period – entering the atmosphere from leaks throughout the natural gas production and supply chain.
The provincial government has supported the LNG build-out with subsidies, cheaper electricity rates, tax exemptions, and other enticements.
At the same time, the CleanBC plan guiding emissions reductions in the province proposes a minimum of 15% of domestic natural gas demand be met by renewable sources by 2030.
To meet this goal, three different technologies could be used – one tried and true, and two still partly on the drawing board.
Right now, a sliver of natural gas demand in BC is met with biomethane from anaerobic digestion. This energy source not only captures methane that would otherwise enter the atmosphere, but uses that methane to displace fossil gas.
Biomethane is produced by refining biogas, which is generated when microbes break down organic matter in the absence of oxygen, creating a mix of methane and carbon dioxide. Biogas is captured in anaerobic digesters – purpose-built plants with distinctive domed tops – that are fed a diet of dairy waste, manure, sewage sludge, or municipal organic waste. A slightly different gas can also be captured from bacterial decomposition of organic waste in landfills. The process has a long history and anaerobic digesters have been used to produce biogas since the late 1800s (even the post-apocalyptic brawlers in the movie Mad Max Beyond Thunderdome managed to get a digester up and running).
Energy potential from anaerobic digestion is basically fixed: there’s only so much sewage sludge or dairy waste produced as a byproduct of human civilization.
Biomethane can stand in anywhere natural gas is used – to fuel a water heater, cement plant, or power a compressed natural gas bus. FortisBC has developed biomethane supply (they call it by a more general term – renewable natural gas, or RNG) with several projects at farms, landfills and dairies. The RNG is added to the gas grid, and ratepayers can opt in to have it replace a percentage of their natural gas use for an additional charge. RNG use is tracked through an accounting system – in other words, customers pay for biomethane credits, while the actual biomethane is commingled with natural gas throughout the gas grid.
Unlike other forms of renewable energy like wind turbines or solar panels, RNG potential from anaerobic digestion is basically fixed: there’s only so much sewage sludge or dairy waste produced as a byproduct of human civilization. In California, for instance, RNG potential is limited to around three per cent of the State’s natural gas demand.
The long-term potential for RNG from anaerobic digestion in BC, as estimated in a study commissioned by the BC government, FortisBC, and Pacific Northern Gas, is 11.9 petajoules per year. For context, the BC Ministry of Mines, Energy & Petroleum Resources told the Watershed Sentinel that 200 petajoules per year of natural gas is projected to be “sold/provided by utilities to their customers” around 2030, indicating RNG in BC would be capped at around six per cent of gas demand.
It’s a gas(ification)
On the horizon, however, is a second way to produce RNG from cellulose-rich biomass feedstocks such as wood waste and straw, using a technology called gasification.
Gasification involves cooking carbon-rich matter under pressure in an oxygen-starved environment. This releases syngas, a mixture of carbon monoxide, hydrogen, and carbon dioxide.
“If you have enough oxygen to completely burn the biomass, that is combustion,” says Tony Bi, a professor at UBC’s Department of Chemical and Biological Engineering and director of UBC’s Clean Energy Research Centre. “If you heat the biomass with no oxygen at all, we call it pyrolysis or thermal cracking. So somewhere in between you use partial oxygen, but it is not enough to completely burn the biomass. That is what we call gasification.”
A second process called methanation recombines the hydrogen and carbon monoxide in the syngas to form biomethane.
The processes are currently used only in demonstration plants, but if the technology can be advanced to commercial scale, RNG potential in Canada will soar.
Bi co-leads a research program to develop biomethane production from forestry wastes as part of the BC Pulp and Paper Bioalliance project at UBC’s BioProduct Institute, a consortium of public and private sector interests. According to the project’s website, mainstreaming biomass gasification has the potential to “replace 50% of Canada’s natural gas consumption and reduce Canada’s greenhouse gas emissions (GHGs) by 108 million tons of CO2 equivalent per year.”
According to the study commissioned by the province, FortisBC, and Pacific Northern Gas, this potential would rely largely on forestry waste feedstocks from sawmills, pulp and paper plants, and logging operations. Of these, the lion’s share of feedstock is from “roadside logging residues” – forester-speak for logging slash.
“It’s a better plan than slash burning and sending all that carbon straight into the atmosphere, but we still need to make sure we’re not depriving our forests of the carbon that they need to regenerate.”
This doesn’t sit right with Mary Booth, the director of Partnership for Policy Integrity, a Massachusetts-based environmental research organization focused on biomass energy and oil and gas extraction. She says net greenhouse gas reductions from forestry waste for bioenergy can take decades, if they happen at all. When wood biomass is used for energy, there is a quick net gain in carbon to the atmosphere. Recapturing that carbon is only meaningful in the time frame it takes the forest to recover to its original state. And because forestry waste biomass emits carbon dioxide whether it decomposes on the forest floor or is used for bioenergy, there is no reduction in emissions except to the extent that fossil fuels are displaced.
If, however, the biomass energy displaces a renewable energy source then there is a missed opportunity to store carbon in that same biomass, build soil carbon, and support forest biodiversity. This subtle catch means the applications for which RNG made from forestry wastes would be applied determine any emissions benefit from the scheme.
Removing logging slash from the forest floor, even though it is considered waste, can also affect the health of a regenerating forest.
“The low-diameter, leafy, twiggy material is where a lot of the micronutrients of the tree resides,” Booth says. “And depending on the soil type, removing waste residues can actually remove a fairly high percentage of the bio-available micronutrients like calcium, phosphorous, and potassium, which are essential to regeneration. So there’s that. And then there’s protection from erosion that leaving the residues offers.”
Tempering these concerns is the fact that much of BC’s logging slash is burned anyway – emitting carbon with no benefit at all.
“I think it’s a better plan than slash burning and sending all that carbon straight into the atmosphere,” says Peter McCartney, a climate campaigner for the Wilderness Committee. “But we still need to make sure that we’re not depriving our forests of that really vital carbon that they need to regenerate after forestry moves through.”
Another big caveat, McCartney adds, is ensuring transport emissions from collecting biomass scattered across BC forests are accounted for.
There is also a third way to partly decarbonize natural gas in BC that uses only water and renewable energy.
Renewable hydrogen, sometimes called power-to-gas, is produced using electrolysis (which splits water into hydrogen and oxygen) powered by renewable energy.
The idea of using hydrogen for carbon-free fuel and as an energy storage medium is nothing new, but unlike in the past, the cost of renewable hydrogen is predicted to plummet. According to reporting on an analysis by BloombergNEF, renewable hydrogen could reach cost parity with fossil natural gas by mid-century, assuming political support bolstered a scale-up of the industry. This could reignite hopes for hydrogen as an integral part of the global energy system.
And according to the UK-based hydrogen energy company IMT Power, available renewable electricity and abundant fresh water make British Columbia ideal for renewable hydrogen. Production sites near deep water harbours would also allow shipping to future export markets in the US and Asia.
If the grid were modified, hydrogen could, in future and in theory, replace natural gas altogether.
Like biomethane, hydrogen is a drop-in fuel which can be mixed with fossil gas in the gas grid – up to a point. FortisBC believes renewable hydrogen could replace between five and 15% of gas demand in BC by 2036.
If the grid were modified, hydrogen could, in future and in theory, replace natural gas altogether. Experts from the Institution of Engineering and Technology, the UK’s engineering professional organization, say it’s possible to re-purpose the entire natural gas system in the UK to carry hydrogen, though technical hurdles would have to be overcome. As proposed, their concept assumes a different way to produce hydrogen by stripping it from natural gas with the resulting carbon captured and stored. However, renewable hydrogen could replace the fossil-derived hydrogen if it was price competitive.
The LNG in the room
For gas utilities, biomethane and renewable hydrogen offer a way to transform their business model to remain relevant in a low-carbon world. In a 2018 report by FortisBC, the company says it will ramp up biomethane and renewable hydrogen to replace 30% of domestic natural gas supply by 2050. They see themselves, says the report, “as an energy delivery company that has climate and economic solutions in the buildings and transportation sectors.”
But part of that delivery is old thinking: positioning BC as a “vital domestic and international Liquefied Natural Gas (LNG) provider to lower global GHG emissions.”
The vision could also end up being largely redundant in light transport, public transport, and buildings, considering the momentum of electric vehicles and advances in building technology and electric heat pumps.
The 15% minimum renewable gas content goal in the CleanBC plan, along with other initiatives, will achieve a GHG emissions reduction of 700,000 tons per year by 2030 – or roughly eight per cent of future LNG emissions.
“The fear is, if we invest in biomethane infrastructure for applications that are ultimately going to be electrified, there could be stranded assets and investments that don’t prove their worth over the test of time,” says Jimmy O’Dea, a senior vehicles analyst for the Union of Concerned Scientists.
This isn’t to say there is no role for RNG. Experts told the Watershed Sentinel that the fuel could decarbonize tough-to-electrify applications such as high-heat industrial processes, chemical and fertilizer feedstocks, long-distance aviation, marine shipping, ferries, remote long-haul trucking routes, and be used in off-grid communities with ready access to forestry biomass.
But that’s all in the future. Whether or not biomethane and renewable hydrogen develop to become a keystone in BC’s decarbonizing strategy, an elephant remains in the room: LNG expansion is expected to produce around nine million tons of carbon pollution annually in BC by 2030, according to the Pembina Institute. To put that in context, the 15% minimum RNG content goal in the CleanBC plan, along with other waste-to-energy initiatives, will achieve a greenhouse gas emissions reduction of 700,000 tons per year by 2030 – or roughly eight per cent of future LNG emissions, by the province’s reckoning. Notably, this does not include the emissions from actually burning the gas.
Put another way, if the province got serious about reining in natural gas emissions, reductions far larger than the CleanBC goal for RNG can be had by not expanding fossil natural gas – no technology needed.
This article appears in our October 2019-November 2019 issue.