By David Dempsey, Karan Titus & Rebecca Peer*
Energy is the double-edged sword at the root of the climate crisis. Cheap energy has improved lives and underpinned massive economic growth. But because most of it comes from burning hydrocarbon fuels, we’re now left with a legacy of high atmospheric carbon dioxide (CO2) and an emissions-intensive economy.
But what if we could flip the energy-emissions relationship on its head? We would need a technology that both generates electricity and removes CO2 from the atmosphere.
The good news is this technology already exists. What’s more, New Zealand is perfectly positioned to do this “decarbonisation” cheaper than anywhere else on the planet.
And the timing couldn’t be better, with the government’s first Emissions Reduction Plan (released Monday) calling for bold projects and innovative solutions.
We research how to burn forestry waste for electricity while simultaneously capturing the emissions and trapping them in geothermal fields. Since forests remove CO2 from the atmosphere as they grow, this process is emissions negative.
This also means a carbon “tax” can be turned into a revenue. With New Zealand’s CO2 price at an all-time high of NZ$80 per tonne, and overseas companies announcing billion-dollar funds to purchase offsets, now is time for cross-industry collaboration to make New Zealand a world leader in decarbonisation.
Bioenergy with carbon capture and storage
Artificial carbon sinks are engineered systems that permanently remove CO2 from the atmosphere.
Bioenergy with carbon capture and storage (BECCS) achieves this by trapping the CO2 from burned organic matter – trees, biowaste – deep underground. An added bonus is that the energy released during combustion can be used as a substitute for hydrocarbon-based energy.
The Intergovernmental Panel on Climate Change (IPCC) has said climate mitigation pathways must include significant amounts of BECCS to limit global warming to 1.5℃. However, the technology is still new, with only a few plants around the world currently operating at scale.
Cost is a major barrier. New projects need expensive pipelines to move the CO2, and deep injection wells to store it underground. Because CO2 is more buoyant than water, there are also concerns that any gas stored underground might leak out over time.
This is where geothermal fields can help.
Geothermal systems for BECCS
Geothermal is a reliable source of energy in New Zealand, supplying almost 20% of our electricity. We use deep wells to tap into underground reservoirs of hot water, which then passes through a network of pipes to a steam turbine that generates electricity.
Afterwards, the water is pumped back underground, which prevents the reservoir from “drying out”. New Zealand companies are world leaders at managing geothermal resources, and some are even experimenting with reinjecting the small amounts of CO2 that come up with the geothermal water.
Herein lies the opportunity. Geothermal systems already have the infrastructure needed for a successful BECCS project: pipelines, injection wells and turbines. We just need to figure out how to marry these two renewable technologies.
We propose that by burning forestry waste we can supercharge the geothermal water to higher temperatures, producing even more renewable power. Then, CO2 from the biomass combustion can be dissolved into the geothermal water – like a soda stream – before it is injected back underground.
Projects in Iceland and France have shown that dissolving CO2 in geothermal water is better than injecting it directly. It cuts the cost of new infrastructure (liquid CO2 compression is expensive) and means reinjection wells built for normal geothermal operation can continue to be used.
Unlike pure CO2 that is less dense than water and tends to rise, the reinjected carbonated water is about 2% heavier and will sink. As long as equal amounts of geothermal water are produced and reinjected, the CO2 will stay safely dissolved, where it can slowly turn into rocks and be permanently trapped.
How do the numbers stack up?
Our initial modelling shows that geothermal BECCS could have negative emissions in the order of -200 to -700 grams of CO2 per kilowatt hour of electricity (gCO2/kWh). Compared to about 400 gCO₂/kWh of positive emissions from a natural gas power plant, this is a dramatic reversal of the energy-emissions trade-off.
Applied to a geothermal system the size of Wairakei (160 megawatts), a single geothermal BECCS system could lock away one million tonnes of CO2 each year. This is equivalent to taking two hundred thousand cars off the road and, at current prices, would net tens of millions of dollars in carbon offsets.
These could be traded via the Emissions Trading Scheme to buy valuable time for industries that have been slow to decarbonise, such as agriculture or cement, to get down to net zero.
Even better, most of New Zealand’s geothermal fields are located near large forests with expansive forestry operations. Estimates put our forestry waste generation at around three million cubic meters each year. Rather than leaving it to rot, this could be turned into a valuable resource for geothermal BECCS and a decarbonising New Zealand.
We can start doing this now
According to the IPCC it is “now or never” for countries to dramatically decarbonise their economies. Geothermal BECCS is a promising tool but, as with all new technologies, there is a learning curve.
Teething problems have to be worked through as costs are brought down and production is scaled. New Zealand has a chance to get on that curve now. And the whole world will benefit if we do.
The success of geothermal BECCS will turn on new partnerships between New Zealand’s geothermal generators, manufacturers and the forestry sector. Forestry owners can help transition wood waste into a valuable resource and drive down gate costs.
Most importantly, geothermal operators can leverage their vast injection well inventories and detailed understanding of the underground to permanently lock up atmospheric carbon.
With the government tightening emissions budgets and investing billions in a Climate Emergency Response Fund, now is the perfect time to make geothermal BECCS work for Aotearoa New Zealand.
*David Dempsey is a Senior Lecturer at the University of Canterbury; Karan Titus, is a PhD Student at the University of Canterbury, and Rebecca Peer is a Lecturer at the University of Canterbury This article is republished from The Conversation under a Creative Commons license. Read the original article.
60 Comments
It is nice that we could do this. Very virtuous.
However,
If we decided to turn everything off tomorrow - immediate carbon zero - what effect would it have on the world's climate?
I'm going to suggest it would have no measurable effect. Nada. A rounding error. China and India would compensate for our disappearance in short order. Meanwhile, our economy and quality of life is utterly devastated.
Interested in counter arguments - would it be worth it?
Yes Green hydrogen has surely got be worth a more detailed look?
I get the economics of transporting it but green hydrogen will carry a premium. Studies I have seen suggest that a useful percentage of our heavy haulage fleet will be running on hydrogen in 5-10 years so there will be a local need anyway.
https://www.hiringa.co.nz/ is not the only group doing interesting things in this area - https://www.nzhydrogen.org/nz-hydrogen-projects
I also think there will be commercial aircraft flying on hydrogen in 8-12 years time.
Hydrogen - and as much as I've looked I've never seen it coloured - is an energy loss. As with a battery, it is energy-negative; merely a storage vector. You have to separate it using some other energy, contain it and transport it ditto. You cannot separate it and deliver it using it - that violates the Laws of Thermodynamics.
And remember that the economic system requires high-quality (of an EROEI of 8:1 or better) energy. Down near 1:1, there is no 'economy', so not trucks trucking, no planes flying. Maybe that is hard to get your head around - but that's how it is.
Can I suggest you can do better than that? Subliminally, that's shooting the messenger.
There ARE best cards to play, in any scenario (including sub-optimal ones). Working out which card is best, requires some thought. 15 years ago, I though we could all live on renewables; the cost was coming down blah blah blah. I have lived that way, ever since and a good deal before; over 2 decades off-grid, ditto low-impact. But the system marched on, ever-closer to the cliff; overshot in systemic ways.
That changes the best card(s) - and now includes defense (as Ukraine is finding out, like Iraq before it and who-knows how many before that). Money is no longer the valid valuation of such things - which is partly why we are in such doo-doo.
But don't shoot the messenger - I do what I do to raise awareness and via that; preparedness.
Go well...
I wonder if you have read some of Steve St Angelo's take on the coming energy cliff. He was the first person I saw use phrases like EROI.
Regrettably a lot of what you say (and regularly get stick for on this website) depressingly makes sense. I suspect we are moving into that phase where we fight over the ever decreasing scraps, with ever increasing consumption and populations. The year I was born (1970) there was something like a 30:1 ratio of oil barrels acquired, to those used to extract it from the ground. I think it has fallen to ~7:1 now. This talk of switching to electric cars usually ignores the fact that the batteries and all the other car components are oil derivatives. How were they made? With decreasing ratios- and greater reliance on more highly processed fossil fuel sources- how will they be made in the coming years?
Nothing 'special', and to be accurate, it will be a shifting goal-post. The attempt to pin down a number, is to point out - correctly - that there is a minimum energy-surplus for maintaining BAU. The first energy-surplus was firewood (took away some of our energy-demand, from food, for digestion). The second was stored grain. Neither are surplus enough to maintain, say, our roading network. That takes more. So ex decay-maintenance, there is a ratio of energy-in to energy-out, which will maintain BAU. Not grow, mind you, just maintain.
Estimates since Charlie Hall (a friend of mine bothered to go stay with him and learn) made the concept mainstream, have ranged from 11:1, down to 5:1. Five is seriously too low; I'll take anything from 8 to 11. The compounding problem is that in trying to keep all these aging balls in the air - the US roading network, the NZ grid, the aeroplane fleet, the runways, the bridges, the pipework, the the the... - takes MORE energy every year (just like maintaining an old vs a new house). So it's an upward return demand, of the energy being supplied. But the supplied energy is reducing in quality. The graphs cross at some number, on some date - but the required-for-BAU number (vs 1) will inexorably increase.
Thus, for the last decade we've been picking in the 8-11 range - but if you ask me about 2030, I'd add 3-5 to current. 2040? May even need over 20:1. See the problem? Luckily, economists have the answer: more consumption, forever, and only regard energy as 5% of your 'economy'. Some of us were just too dumb to understand this....
:)
Green hydrogen is an expensive way to move things around and only works for cases where batteries do not work - currently long-haul flights, trucking and shipping.
You will pay a lot of money and divert a lot of energy generation resources into creating green hydrogen (you need to generate more than 3x the energy you get back).
The only workable use case is for soaking up excess generation from renewables that would otherwise be wasted. Arguably, pumped hydro is a better option here but the advantage is that hydrogen can be created locally rather than centrally.
This is essentially the tragedy of the commons. Why should we do anything when we're just a small part of the problem?
The simple fact is that we all need to act. Sitting this one out and hoping the bigger boys do the work for us is not only a pathetic abandonment of our responsibilities as a high per-capita emitter, but will in time make us an international pariah. We either stand together or we fail.
That is a total oxymoron - so James Shaw!
Your economy is an energy/resource-flow construct. Did you read my article?
https://www.interest.co.nz/public-policy/115678/murray-grimwood-outline…
We can do the best in the circumstances - and should - but we won't identify 'best' from your angle.
Agreed. If we know that there is no or little intention to act (see China, India), what is the point?
Would our money not be better spent preparing for climate change rather than trying to prevent it (knowing it is probably hopeless).
Also, I can't help but think that our leaders don't really believe climate change is going to be devastating. If they did, we'd stop buying from dirty manufacturers (who often subject their workers to human rights abuses). It seems to me that our leaders want to appear to be doing something, to hurt the economy a bit (it's got to feel real..), without treating the issue with the seriousness they claim it deserves.
A lot of the actions are things we will be forced to do sooner or later, or should be doing for other reasons. We will have to move away from fossil fuels at some point because they will run out. We should move away from ICE vehicles and other similar emissions sources because of the huge health impacts of polluted air. We should promote active transport because sitting our cars rather than walking or riding a bike shortens our lives and reduces our quality of life. Reducing our single use plastic waste and other waste sources reduces the number of sites we have to destroy with landfill.
Yesterday I made this argument as well. And it is still true that our contribution to global warming is very, very small. And therefore it is also true that removing our emissions is of no real effect.
However let us judge this idea on it's merits. In my role business cases must first align to our values and then provide a rate of return above the CoC hurdle rate and risk/return assessment. On this basis this project makes sense no matter its environmental impact.
Aligned to values? Yes (unless global warming is a hoax, and yes we have those folk here).
Rate of return? A interesting one, no details resolved here but there seems confidence that the costs will be covered by the raising revenue of offsets. I have no more information on this but it looks promissing.
Risk assessment? Again an interesting one, but the risks of the technology not working seem low and given we have already the majority the infrastructure the cost exposure relative to potential upside seems warranted.
How about this:
- the countries who are most onboard with addressing climate change are usually the wealthiest (per capita)
- the ones that are doing the least, are developing still
So, in a world where we can't be all things to everyone due to our size, it'd make the most economic sense to align our industry towards pleasing the first group over the second.
Thats aside from any moral view.
Agree - but only to the extent that we align enough to still be able to trade with those nations while not crippling us economically (and concentrate wealth in the hands of a few, possible external, actors). I recall the NZIER analysis on the carbon free 2050 proposal, which found that we'd sacrifice 20% of GDP by then, the cost falling disproportionately on the poor.
Reducing emissions locally is one part of the solution but in doing so developing new technologies that can be licensed or sold overseas is where we should be putting our money.
The Nordic nations champion this: there has been no knee-jerk clampdown on their mining sector; instead those operations are heavily taxed and the proceeds are diverted towards clean-tech research & commercialisation initiatives.
In short, build a sizeable high-value production ecosystem around clean-tech and then phase out polluting sectors.
"Meanwhile, our economy and quality of life is utterly devastated" - how do you know it isn't the other way around? I can definitely see an outcome where our economy is devastated by people/countries not wanting to buy our goods because we have one of the highest per capita emissions. Doing nothing is not guaranteed to keep our economy safe.
redcows,
Two points. Is making the world greener and more sustainable not a worthwhile aspiration anyway? Do you really believe that anthropogenic global warming is a myth?
We can argue about just how much oil and gas we still have, but surely there can be no argument that in practical terms, we will run out at some point, so climate change or not, we have to start the transition. No?
The redcow argument answers itself.
'More sustainable' says, by inference, that it is not fully sustainable. It will therefore cease; later than 'fully unsustainable', but cease it will.
Fully sustainable is the only valid goal. It requires 100% recycling (we choose not to allocate energy to that, even now). It requires no draw-down of stocks or capacities; finite, renewable or sink.
We are hell-and-gone from that threshold.
Sorry, I thought by shouting the last sentence I would make my self obvious. Obviously not.
I am In Total agreement, especially with the climate change or not. I'm a denier of CC simply because I think it's a red herring not worth debating. We simply cannot carry on digging up resources. It must end.
Why not both? They are talking about using forestry waste, not the usable timber.
I imagine the trouble will be making enough money from the process to pay for collecting and transporting all the waste from tricky forestry blocks that is currently abandoned and left to rot, but it sounds great.
Exactly the cost of gathering and transportation of the waste would be substantial not to mention that CCS is very much unproven at scale. Coal industry has been trotting this red herring out for years . Also nutrients lost by the forest need to be replaced for the next crop so transferring them to be burned has a cost .
.
Indeed, this seems like a challenge however there is a lot of forestry around our Geothermal plants (they are based in our forestry region) so hopefully this can be avoided by using electric trucks etc. They also mentioned re-integrating the existing CO2 release from hydrothermal as a first step, not sure of the % scale of this.
Interesting. Another model. Just like the IPCCs wonderful models.
"*David Dempsey is a Senior Lecturer at the University of Canterbury; Karan Titus, is a PhD Student at the University of Canterbury, and Rebecca Peer is a Lecturer at the University of Canterbury "
No disciplines for these lecturers. Maybe it'll reveal their alignment. Perhaps Canterbury Uni is now employing some pro man made CC specialists to get onto the CC handout gravy train.
Probably none with any financial experience. But wait once the initial concept is expected now we need to cost That'll be an additional grant. Not that I'm opposed to spend money to see if you need to spend money, but in this instance no.
Pressure makes quite a difference to how much CO2 can be dissolved, and since they have to pressurize the water to pump it back underground anyway, then there's no added cost to putting the CO2 under pressure as well.
Take a look at the nonsense on Youtube re Coke and Mentos. It helps to demonstrate how much CO2 even moderate pressures can capture.
Having a reread, I see what your saying. The energy used to pressurise the CO2, could be used to pump the water underground. So no extra energy used. But would that amount of energy be enough to capture that amount of CO2. As the wood fuel is carbon neutral, (yes,pdk, I know not 100%), any CO2 so stored is a net saving. Just not convinced this is anywhere near a countries salvation, as the author seems to be pitching.
In broad terms, we haven't sequestered because it would have taken too much of the energy - and we selfishly wanted all the energy to ourselves, now.
And that was with high EROEI energy - much surplus or profit energy. We are staring down the barrel of a lot less energy - I think we will be burning the wood-waste to keep warm, and it may be that it is less energy-requiring to migrate to where the trees are...
And a quick question - see all those pipes in the photo? Do you think, 50 years from now, we are building/maintaining such stuff on solar energy? Or geothermal electricity? It has never been proved that we can.....
Carbon is just one building block for all organic matter. The carbon content (living biota and organic matter) in NZ pastoral soils is between 60-100 tonnes/hectare. There's been quite a lot of research in this area, not so much for conifer forests. In the case of trees the other building blocks are drawn from the soil.
The point is that growing biomass is a dynamic process with cycling of organic matter back into the soil, critical to the long term sustainability of the soil resource. If most tree mass is removed, an important component of biomass is prevented from recycling into the soil and providing the feedstock for myriad microorganisms that make soil function.
When considering innovations such as that proposed, care needs to be taken to ensure that a "robbing Peter to pay Paul" situation is avoided.
It's easy to consider forest harvest slash as waste because it can look a blot on the landscape. And it's easy to view soil as dirt. The reality is that the soil is a living resource that needs to be fed and slash is an important organic feed source in forestry systems.
One slight problem is "Forestry Waste" is actually a very small volume - it may look a lot but most is air between branches and very expensive to collect.
if Fonterra and others burn biomass they will need around 4 million tonnes plus of wood fibre per annum - The Chinese log customers arent going to take to kindly to losing that volume.
If people want to burn this wood they had better get talking to the forest industry pronto. Fonterra are already pushing us to plant more trees asap for them. Hill country farmers don't want any trees planted - The ERP just announced they (the Crown) will plant 10,000 ha of forest for for biomass (Where??) - someone wake me up when they finally decide what they want!!!
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