Category Archives: climate change

Germany Reaches Renewable Energy Milestone

Posted on by
Reply

The drop in demand for electric power due to the Covid-19 pandemic helped Germany reach an environmental milestone in 2020: For the first time more electricity from renewable sources was fed into the German grid than from fossil fuels and nuclear combined.

50.5 percent of the net electricity production came from wind, solar, hydro and biomass vs. 49.5 percent from fossil or nuclear. Wind power alone accounted for 27 percent of all electricity, more than brown coal and hard coal combined (24.1 percent).

2020 numbers for Japan are not yet available, but in 2017 renewables excluding hydro power accounted for only 8.1 percent of the Japanese electricity production, with hydro providing another 7.9 percent. 39.5 percent came from LNG, 32.7 percent from coal 8.7 percent from oil and 3.1 percent from nuclear.

Japan’s power generation plan for FY2030 foresees only 1.7 percent for wind power, 7 percent for solar and an overall share for renewables (including hydro power) of 22-24 percent of the total. That is less than half the share that Germany achieved in 2020, a whole decade before Japan.

Toyota is yielding the future to Tesla and other EV makers

Posted on by
Reply

In October 2019, Toyota along with General Motors and Fiat Chrysler sided with the Trump administration in its effort to strip the state of California of its ability to set tighter vehicle emission standards than set by the Federal government. In July 2019, several other car makers including Ford, Honda and Volkswagen had sided with California.

This seemed a very odd move for a company whose iconic Prius hybrid was once seen as a way for people ranging from middle class families to Hollywood stars to show their green credentials. Toyota seems on the wrong side of history now.

I also drive a Prius which I bought almost 12 years ago. When it came out, it was way ahead of everything else: Three times as fuel efficient but more spacious and more reliable than my Audi. It wowed me when I first saw one and later when I first test-drove a friend’s. As an engineer I appreciated the clever technology behind it and as a family man I could rely on it for affordable transport.

However, if I were to buy a car now, I’d have a hard time making up my mind. If Tesla had designed its Model 3 as a mid-size hatchback (like the Prius) instead of giving it a trunk, the choice would be easy. Tesla seems set to address that criticism with its forthcoming Model Y, which will be like a slightly larger hatchback version of the Model 3. If Toyota had redesigned its Prius as a battery electric vehicle (BEV) with at least 300 km of range, the choice would have been even easier. The problem is, Toyota isn’t going to do that and I think I understand why.

I have talked to Toyota dealer sales representatives who came to sell me a new Toyota and when I mentioned about electric vehicles, they kept telling me the time wasn’t ripe for that yet, that infrastructure was too spotty and range too short. I would be better off getting another hybrid as the next car. And Toyota has many hybrid models.

This is precisely the problem: Toyota kept enhancing the hybrid drivetrain of the Prius, improving fuel economy with every new version. Now many different models, from the Toyota Aqua / Prius C to the Corolla Hybrid to the JPN Taxi basically all use the same family of engines, gearbox, battery, inverter and other electric systems. This has kept development costs low and maximized economic gain from the numerous patents that Toyota has received for the Prius.

Meanwhile, Tesla appeared on the scene as a complete outsider and took a radically different approach. By going for an all-electric drivetrain they don’t need an Atkinson-cycle internal combustion engine (ICE), an electrically controlled planetary gear transmission and many other mechanical parts that make the Prius family unique. They just need a bodyshell, an electric motor/generator, inverter and battery. For the first models the battery was basically built up from the exact same “18650” cells that power laptops and the bodyshell for the Tesla Roadster was bought in from Lotus.

Batteries for the automotive market are made by specialized suppliers such as Panasonic and LG instead of being based on in-house designs and intellectual property such as ICEs or gearboxes. Motor/generators and inverters are much simpler and less proprietary than ICEs. The basic technology for inverters used in BEVs and the electric part of hybrid drivetrains has been around since before the 1960s. Toyota engineers got the inspiration from the electrical systems used in bullet trains (shinkansen) that launched before the 1964 Tokyo Olympics.

If current owners of conventional or diesel cars replace their aging vehicles with hybrids then Toyota and its stable of Prius and cousins will do very well. If people however take a good look at the ecological realities of the 2020s and beyond, they will see that the sooner we can stop pumping more CO2 into the atmosphere, the less catastrophic our future will be on this planet. If we still drive cars, they will have to run on renewable energy sources, which hybrids can’t do (except plug-in hybrids for relatively short distances).

This raises a second issue: Toyota has been betting on hydrogen as the fuel of the future. Its Toyota Mirai runs on compressed hydrogen (H2), which is converted into electricity in an on-board fuel cell. This gives it a range of about 500 km between refuelling.

If Toyota were to sell BEVs with ranges of 300-450 km, this would undermine the rationale for hydrogen cars which need a completely new infrastructure for refuelling. Each H2 station costs millions of dollars and the fuel is expensive.

The most economical way of making hydrogen is from natural gas or coal, which releases greenhouse gases. Though one could make hydrogen through electrolysis (splitting water into hydrogen and oxygen using electricity), because of inefficiencies inherent in this process, this would actually consume about three times more renewable electricity than covering the same distance by charging/discharging a battery. This is why hydrogen will ultimately remain an automotive dead end.

What hydrogen technology basically gives Toyota is a political fig leaf: They can claim to have a path into a carbon-free future that does not rely on batteries (like Tesla and others). Using that fig leaf they think they can keep selling cars that burn gasoline, in California and elsewhere. Perhaps they can hold off moving beyond hybrids for years and years to come. If they can keep selling what they’ve got they may make healthy profits in the short term, but for the sake of the planet I hope this plan won’t work.

I’ve seen this movie before. In the 1990s Sony launched its MiniDisc (MD) player as a replacement for analog audio tapes and recordable alternative to digital Compact Discs (CDs). Then, in the late 1990s MP3 and flash memory came along: smaller, cheaper, more simple. The whole strategy fell apart. Sony could have accepted that MP3 was a superior solution, but that would have then put them on a level with every other audio consumer product maker. Their patents on MD would have become worthless. So they struggled on with trying to promote MD until they eventually had to kill it. From the inventor of the iconic Sony Walkman that had created a whole new market and sold the brand name to billions of consumers, Sony turned into a company that had lost its way. It let newcomers such as Apple with its iPod (which soon morphed into the iPhone) take over the market and consumer mindshare. The rest is history.

So if you’re listening, Toyota: Please build a car as spacious, practical and reliable as the Prius, but without a hybrid drivetrain that still releases CO2 with every km driven. Make it a no compromise battery electric vehicle. Support vehicle-to-grid technology, in which parked cars have an important role to play for stabilizing the electrical grid. Instead of working with fossil fuel companies to turn fossil fuel into hydrogen for thousands of yet to be built H2 filling stations, support expanding renewable power production from solar, offshore and onshore wind, geothermal and large scale storage, which is what we will need for a carbon-neutral future.

Meanwhile, when the time comes to replace my 12 year old car I will look at all the battery electric hatchbacks on the market then. If there is no Toyota amongst them then my next car will not be a Toyota. It’s as simple as that.

The Runway to Hell

Posted on by
Reply

Even four years after the Paris climate agreement, politicians, businesses and consumers are still in denial what this means for our future and what we must do today. At best, we’re all paying lip service while trying to postpone making real changes.

Two examples: Narita airport is planning for a major expansion in flight capacity in the 2020s and Tepco and Chubu Electric Power are trying to open a new coal fired power station in 2023.

One of the greatest concerns behind climate change goals are climate feedback loops, where any amount of additional global warming triggers new causes of global warming. A few examples:

  • If arctic temperatures rise enough for the ground in permafrost regions to thaw in the summer this will lead to CO2 and methane releases from frozen ancient organic matter that starts to rot and decay.
  • Warming oceans may release methane trapped in icy slush as methane clathrate on the sea bed.
  • If summer air temperatures on the Greenland ice sheet rise enough to melt snow during daytime before freezing again, it changes the albedo of the frozen surface to absorb more sunlight and melt again more easily.

So if we want to avoid runaway global warming, we have a very tight CO2 budget that we can still release before the world has to run on 100% non-fossil energy sources.

What we would need is a moonshot-like project, with our brightest minds and financial resources focused on switching all power generation to non-fossil energy, expanding it to take over from other uses of oil and gas such as transport while minimizing release of CO2 outside of power generation. That means not just electric cars and trucks but also fewer cars, less air travel, no more deforestation, minimal consumption of cement and steel and more recycling.

While the Japanese government has formally committed itself to fighting climate change, the reality looks different. Last year the Narita International Airport Corp., government ministries and local government agreed to a plan to increase annual takeoff and landing slots from 300,000 to 500,000. To this purpose, a 2,500 m runway will be extended to 3,500 m to handle bigger planes and a third runway of 3,500 m will be built in the 2020s. Currently, there is no practical alternative to kerosene-based jet fuel. More flights and bigger aircraft mean more CO2 emissions from fossil fuel. Instead of making it possible for more people to fly more often, we should be looking for ways to discourage and avoid flying wherever possible.

JERA, a joint venture between Tepco and Chubu Electric Power is trying to build a coal-fired power station at Kurihama near Yokosuka, with plans to start operating in 2023. Coal is the most carbon-intensive of all fossil fuels. One kWh generated by burning coal even in the most advanced coal-fired thermal power stations releases about twice as much CO2 as the same amount of electricity generated from a combined cycle gas turbine (CCGT) power station running on natural gas. With a limited carbon budget it makes no sense to burn any coal if we still have gas. If we really still must expand fossil fuel power generation (and we probably don’t in Japan), coal is by far the worst choice of all fossil fuels available!

Instead of expanding airports and building coal power stations, we should expand offshore wind power and geothermal energy while raising taxes on air travel, for example by taxes on jet fuel. A recent International Energy Agency report estimated the worldwide potential for wind energy production at 11 times the annual electricity consumption of the world. Japan has almost completely blocked offshore wind power. It has a huge Exclusive Economic Zone (EEZ), yet in 2018 Britain’s installed offshore wind power base was over 120 times that of Japan, Germany’s about 100 times and China 70 times. Even Belgium which controls only 0.5% of the North Sea had 20 times more installed offshore wind power capacity than Japan in 2018.

Some air travel can be shifted to trains or to less energy intensive ships. Eventually we will develop technology to fly airplanes with non-fossil fuel, such as methane produced from CO2 with renewable electricity in reverse fuel cells though that won’t be cheap or particularly energy-efficient. But until then we need to make hard choices that take us closer to our goals, not further away from them.

Future generations will struggle as coastal land where hundreds of millions of people worldwide currently live or where they grow food will disappear in the sea as warming oceans expand and glaciers melt. They will have to deal with it.

Whole countries will disappear in the next couple of centuries, including the Netherlands and Bangladesh. The same will happen to most of the ten largest cities in the world. The sea level rises projected until 2100 are by no means the end of the story: Sea level rises for several centuries to come are already locked in with the emissions of the last 200 years. The last time this planet had more than 400 ppm of CO2 in its atmosphere (as opposed to 280 ppm before the industrial revolution) was 3 million years ago, when sea levels where 20 m higher than today. So that’s going to happen again, even if we stopped burning all coal, oil and gas today. But because we are still going to keep doing that for a number of years or decades, the ultimate sea levels will be even higher than they were then.

Maybe in some ways it’s easier to speak truth if you’re a 16 year old school kid, not a politician who wants to get campaign finance from friendly businesses or to get reelected by voters who still want to fly on vacation to Thailand, or a business leader trying to please shareholders instead of saving the planet. But reality is reality, even if we look away. We, or our children and their children, will have to face it eventually and it will be what we make it today.

It Takes a Child to Raise a Village

Posted on by
Reply

A few years ago I was visiting Venice. It was a fascinating experience to walk around this ancient city without cars, built on some islands in a lagoon that protected it from the chaos after the fall of the West Roman Empire. I was surprised how eastern some of the architecture looked, because I hadn’t known how tight the connections were between Venice and the Byzantine empire, the successor state to the East Roman Empire. More than a thousand years of history come alive when you walk those ancient cobble-stoned streets.

For a long time Venice has been slowly sinking into the sea. In many buildings I saw, the ground floor was more or less uninhabitable and ruined due to water damage or the risk from regular flooding during storm surges. Sadly, despite all efforts to save it, Venice will disappear in the ocean, gradually swallowed up by rising seas.

The same will happen to Amsterdam, once the capital of a trading nation from where ships sailed to every continent. And not just this city will disappear, but almost the entire country of the Netherlands. It’s not a question of if but when.

Its inhabitants will gradually migrate to other countries in Europe, such as Germany, France or Spain that will be less affected by a 20 m rise of global sea levels. The Netherlands will be virtually wiped out when that happens. So will be Bangladesh and many island nations, as well as Miami, Shanghai, Bangkok, Jakarta, much of Tokyo, London, New York City and many other coastal megacities around the world.

When I was a schoolkid, I learnt from science books that 0.3% or 300 ppm of the earth’s atmosphere was carbon dioxide (CO2). I wasn’t told that only 200 years earlier, before the Industrial Revolution it had only been 280 ppm. Later I learnt that CO2 is a so called “greenhouse gas”, as it traps heat from the surface of the earth and prevents it from escaping into space, thus raising the surface temperature of the planet. As our civilization burns coal, oil and gas and clears forests the CO2 level increases and the greenhouse effect intensifies. In the last couple of decades this has been happening at an increasing rate.

Last year the world consumed about 100 million barrels of crude oil a day. 99.6% of passenger cars on the roads worldwide in 2018 run exclusively on fossil fuels. Worldwide power generation from coal is growing rapidly and is expected to double from 2011 to 2023. Of all the fossil fuels, coal releases the highest amount of CO2 per kWh produced, yet many countries are still building new coal-fired power plant capacity, including here in Japan, where a TEPCO – Chubu Electric Power joint venture still wants to open a new coal-fired power station in Kurihama near Tokyo in 2023/2024.

In 2013, the 400 ppm level was already breached and it is still rising at an increasing rate. How significant is that number? Since humans walked on this planet it had never been as high as this: You have to go back millions of years to find an era when there was as much CO2 in the atmosphere: The last time the CO2 level was above 400 ppm was in the Pliocene (about 3-5 million years ago).

At that time the average global temperature was some 2-3 C higher than today, but temperatures in the arctic and in Antarctica were significantly higher than that. Trees were growing in the southern part of Greenland, which was not covered in thick glaciers as it is today. Trees were also growing in parts of Antarctica. Without billions of tons of water locked up in glaciers in Greenland and Antarctica, sea levels were 20-25 m higher than today. Also these oceans were warmer than today and water expands when it warms up. The rising CO2 levels will melt these glaciers again, until a new equilibrium is established several hundreds years or more in the future. The coast lines will move, gobbling up cities and farm land alike. Ultimately they may well look like those in the Pliocene again, but how much ice will melt and how rapidly it will melt still depends on what we do from now.

To give you an idea of the long term impact of this kind of sea level rise, the former Chinese capital of Nanjing, 200 km from the Yellow Sea, lies only 20 m above sea level. With 25 m of sea level rise the ocean would penetrate about 180 km inland southwest of Beijing. Some of the most densely populated areas of China (national population: 1.3 billion) would be swallowed by the sea.

In Vietnam the two biggest cities, Hanoi and the Red River plain around it, and Ho Chi Minh City (Saigon) and all of the land southwest of it will drown. Many of Asia’s river plains that are now its biggest rice baskets will turn into continental ocean shelf. The same will happen in the Nile valley or along the Euphrates and Tigris in the Middle East.

Note that these are changes that will happen over the next centuries or more regardless of what we do from now. They are the least bad outcome of what is possible. If we do nothing, it will get far worse.

There are feedback cycles that amplify the negative effects. For example, once it gets warm enough in summer in arctic permafrost regions that the ground will melt in summer, then peat and other frozen organic matter in the wet soil will start to decay, releasing huge amounts of methane, an even more powerful greenhouse gas than CO2. This in turn will raise temperatures even higher. Where white sea ice melts in the summer, darker ocean water is exposed below, leading to more sunlight being absorbed and higher air and ocean temperatures. This in turn leads to less sea ice coverage the next year. When snow on top of glaciers thaws and refreezes, it also changes its albedo. The ice absorbs more sunlight than the virgin snow. So every warm spell leads to more warming. Once the thick ice sheet in Greenland and East Antarctica starts melting, its elevation will drop. It’s colder at higher elevations. The reduction in thickness will speed up melting. We could end up with a run-away effect that is impossible to stop until there is no ice left (see this article in National Geographic for maps of what the world will look like then).

The young Swedish climate activist Greta Thunberg, who started campaigning against inaction against climate change as a 15-year old, used the image of a “house on fire”:

Our house is on fire. I am here to say, our house is on fire. […] Adults keep saying: “We owe it to the young people to give them hope.” But I don’t want your hope. I don’t want you to be hopeful. I want you to panic. I want you to feel the fear I feel every day. And then I want you to act. I want you to act as you would in a crisis. I want you to act as if our house is on fire. Because it is.

The changes brought about by man-made climate change will be dramatic, but political action so far has been underwhelming. The steps taken so far or even the steps discussed in public fall far short of what is necessary to avoid even worse outcomes.

There is considerable resistance to taking action against Climate Change. We are not used to thinking much about events beyond our own life time. Politicians will worry about the next elections, business leaders about their next annual business results. Politicians tend to take drastic action only in wars and other major disasters, but Climate Change is going to be bigger than any (non-nuclear) war or hurricane.

If we were honest and ethical, we would not put the stock market value of our power companies or car or airplane manufacturers or our airlines or tourism industry above the future of the planet. The resistance to change from both industry and consumers will be huge, but we owe people the unvarnished truth: That we can’t continue with business as usual.

Even if we switch to electric cars, the steel, copper and glass for those cars for now will be made using fossil fuels. Even the wind turbines, solar panels and battery storage that we have to build at a massive scale to supply renewable energy for our future civilization will largely be manufactured using fossil fuels for years to come. We have to spend our dwindling carbon budget wisely, for example on rebuilding infrastructure instead of on holidays in Bali or a shiny new BMW SUV.

There is as yet no clear technical solution for air travel or for international cargo ships without fossil fuel. The same is true for making cement or for steel production from iron ore. In the short term we could replace kerosene or heavy fuel oil with LNG to reduce CO2 output in transport, but that is not enough and we will need to go much further than that. The next steps will be much harder. We don’t have the solutions yet. Therefore we need a modern moonshot program for a post-fossil future, an all-out effort — not to put more humans on the moon again — but to decarbonise our economies.

Over the last year Greta Thunberg has become a household name worldwide. She has drawn attention to the urgency of change and to the drastic nature of the changes needed. Her youth and thus her expected life span versus those of the politicians and business leaders of today, who mostly won’t be around after the year 2050, gives her a different perspective which the rest of us can then also relate to. It’s not all about us, but about our children and all of humanity after us. Sometimes it takes a child to educate the world.

Water Abundance XPRIZE – Do the Numbers Add Up?

Posted on by
Reply

On October 22, 2018 a US$1.75 million prize was awarded to two companies for a way of providing abundant water at a price of no more than $.02 per liter using renewable energy.

The technology developed by the Skysource / Skywater Alliance condenses humidity from the air using electrically powered compressors. It’s basically the same process as in a domestic air conditioner unit that has water dripping out of it, except that the Skywater units will filter and then sterilize the water using ozone. Condensation through a compressor is an energy intensive process.

There are other processes for generating fresh water from abundant sea water that also have a reputation for consuming a lot of energy. Desalination is used by many coastal cities and regions to top up insufficient ground water supplies. About of half of Israel’s water supply comes from Reverse Osmosis (RO) plants that desalinate sea water from the Mediterranean. Desalination plants also provide about 30% of Singapore’s water supply.

Reverse Osmosis consumes about 3 kWh of electrical energy per 1000 liter (1 m3) of fresh water extracted. If produced from fossil energy sources such as coal, oil or natural gas this energy demand will result in CO2 output, contributing to global warming. If produced from renewable energy, it requires considerable investments in generating capacity on top of the desalination plants themselves.

How does the Skywater process compare to RO with regards to energy consumption? The Skywater website is not exactly helpful, as it present gibberish instead of actual data:

What are the power requirements for the machine?
The Skywater® 300 runs on approximately 7 -10 kilowatts per hour. It operates on 50hz or 60hz and either 208-240V (single phase) or 380-440V (3-phase). This power can be supplied directly or from a generator for portability.

The Skywater 300 is a unit that can generate up to 1100 l of water per day. The above quote was neither written nor checked by an engineer. Note that energy is measured in kilowatt hours (kWh) while power is measured in kilowatts (kW). There is no such unit in physics as “kilowatts per hour”. Whoever uses this term basically doesn’t know what they are talking about! A device drawing one kilowatt of power will consume one kilowatt hour of energy for every hour of use.

Let’s assume they meant a power demand of 7-10 kW (which is the same as 7-10 kWh per hour). That means a daily consumption of 168-240 kWh of electricity. With an output of up to 1100 l, this amounts to at least 150-220 kWh per 1000 l (1 m3). This is roughly 50-70 times more than the specific energy consumption of a Reverse Osmosis plant. Other commercial units of water generators have similar specs. For example the units offered by Water-Gen in Israel are quoted as consuming 310 kWh per 1000 l, or roughly 100 times the power consumption of reverse osmosis units.

Today we’re still a long way from having access such an abundance of cheap electricity from renewable sources that we could afford to use 50-100 times more of it than another proven solution would use. Installing solar panels or wind turbines to power RO plants is expensive and consumes land. Building 50-100 times more solar farms or wind turbines to generate the same amount of water using water-from-air technology instead would make little sense, at least within a reasonable distance of the coast where you could still pipe desalinated water from coastal RO plants.

Water-from-air technology may make sense only in limited areas such as mobile military units in remote areas where cost is no object (but only if humidity is not too low and it’s neither too hot or too cold, i.e. if they’re not deployed in a desert anyway).

On the present evidence, water-from-air technology is far from ecologically benign or economically viable, compared to more efficient technologies available. The first step would always have to be reduced use of conventional water supplies (e.g. better irrigation systems, growing less water intensive crops) encouraged by appropriate pricing and reuse of waste water for other purposes.

Carbon Sink Concrete Snake Oil

Posted on by
Reply

When I was a kid, I learnt that carbon dioxide (CO₂) makes up around 0.3 % (300 ppm) of the atmosphere. Man-made CO₂ output, from burning of fossil fuels to deforestation, has increased this number year after year. In 2013 it first exceeded 400 ppm. Even back in the 1950s, after over century or coal and oil burning, the number was already the highest in 650,000 years. We are still adding CO₂ to the atmosphere every year and the amount being added per year is still increasing. As CO₂ is a heat-trapping greenhouse gas, this has far-reaching consequences. There are dangerous feedback loops that will amplify the consequences, from increased arctic warming from absorbed sunlight due to melted sea ice to increased methane output from melted permafrost regions. Disappearing mountain glaciers will have effects on rivers downstream.

As humanity realizes the dangers from changing climate, from rising sea levels to extreme weather patterns, devastating droughts and wildfires, desertification and failing harvests we need to take action. We will need to cut CO₂ emissions as much as possible as soon as possible, but we also need to look at ways of binding CO₂ that has already been released.

Some people are trying to make a quick buck on this or to deflect consequences from industries that harm the environment. Because of this, be very skeptical of any claims made for carbon sink technologies that aim to delay the phasing out of fossil energy sources (including but not limited to “clean coal”).

A couple of years ago a US company called Calera made headlines with bold claims of a process that could act as a carbon sink for CO₂ from fossil fueled power stations while producing a product that could be used in place of cement. About 5 % of global CO₂ output is from cement production while power stations account for about 1/3 of CO₂ output in the US, therefore this would sound like a win/win situation. The process would extract calcium from sea water, combine it with CO₂ from the smoke stack of a power station and output calcium carbonate (lime stone) as a building material. Calera received funding from ventures capital fund Khosla Ventures and built a prototype plant adjacent to the Moss Landing power station at Monterey bay, California.

The company has always remained fairly tight lipped about how its process would actually work and what its inputs and outputs would be. However, despite the numerous articles that repeated its ambitious claims, nothing much seems to have come off it since.

The fact is, their claims were debunked by two critics, Jerry D. Unruh and Ken Caldeira, but relatively little attention was paid by the media to the inconvenient facts they had pointed out.

Most of the calcium and magnesium dissolved in sea water is either in the form of calcium bicarbonate or magnesium bicarbonate. To precipitate dissolved (Ca,Mg) bicarbonate as solid (Ca,Mg) carbonate, one has to remove CO₂, not add it. Calcium and Magnesium dissolved in the ocean is there because rain water absorbs CO₂ from the atmosphere and then dissolves lime stone and dolomite rock as it seeps down into the ground before re-emerging in springs and rivers:

H₂O + CO₂ + CaCO₃ => Ca(HCO₃)₂
H₂O + CO2 + MgCO₃ => Mg(HCO₃)₂

Precipitating solid carbonate from dissolved bicarbonate reverses the process and thus releases CO₂:

Ca(HCO₃)₂ => CaCO₃ + H₂O + CO₂
Mg(HCO₃)₂ => MgCO₃ + H₂O + CO₂

Fundamentally, calcium and magnesium ions (Ca++, Mg++) in sea water are not a viable option for binding millions of tons of CO₂ as they are already the end result of a carbon-binding process. Turning bicarbonates into carbonates either releases CO₂ or it requires huge amounts of alkaline materials to bind that CO₂.

The truth is, besides CO₂ and seawater, Calera’s prototype plant consumes existing stocks of alkaline magnesium oxide left over from previous industrial uses at the site, but those stocks won’t last forever. If one had to replenish these stocks from scratch year after year, this typically would involve the high temperature calcination of magnesium carbonate, which consumes roughly as much energy and produces as much CO₂ as making cement does.

Calera has suggested a few alternatives in place of magnesium oxide as alkaline process inputs for a full scale production system, but these don’t make much more sense either:

  • Making sodium hydroxide from brine via electrolysis consumes more electricity than can be produced from any power station whose CO₂ this process could clean up.
  • Fly ash from power stations can be a low cost source of alkalinity, but only in the case of relatively carbon-heavy coal and not natural gas. Even there the amounts of ash are far too small relative to the amount of CO₂ to be absorbed from burning the coal. Cleaning up CO₂ from coal using fly ash still leaves you with more CO₂ than burning natural gas without cleanup.

Long term, the cheapest way of dealing with rising CO₂ levels are not carbon sinks, but not producing the CO₂ in the first place. This means reducing energy consumption, a halt to deforestation, switching transport to electricity and producing power from wind, solar, geothermal and other non-fossil energy sources. The sooner we do this, the more livable this planet will remain for its 7 to 12 billion inhabitants this century.

Further reading: