Carbon sequestration is in the news with more interesting ideas on how to reduce the CO2 (carbon dioxide) content of our air. The ideas range from hopeful to hopeless, from well researched but not yet tested through to ideas that might be funny if you could ignore the fact that people wasted their brain cells working on the idea. Some ideas are clearly useless scams designed to make a company rich.
The average person produces 25 tons of carbon dioxide per year according to some people and estimates vary from 15 to 40 tons. The metric tonne is slightly different but comparable to the imperial ton for our purposes.
Hummers burn more fuel than Hondas. Houses in cold climates require more heating than houses in temperate climates and badly designed tropical houses burn massive amounts of carbon trying to keep the air cool. Either driving a Hummer or owning a house in northern Canada could put you in the 40 tons per year while driving a Hummer and owning a house in a cold climate could put you up to 60 or 70 tons per year.
One ton of carbon produces 3.7 tons of CO2 because each carbon atom gains two oxygen atoms and oxygen is heavier than carbon.
Dump CO2 in the Ocean
There are companies showing plans for complex systems that ultimately dump the CO2 in the ocean. This sounds like the old idea of dumping radioactive waste in the ocean. Search for Minamata to find another example of dumping pollutants into the sea.
The ocean already accepts huge amounts of CO2 from the atmosphere and returns excess CO2 when the water warms up. You can see the equivalent return process by experimenting with a glass of soda water. Watch the CO2 bubble out as the water warms up.
We could pump more CO2 into the ocean deep down in the cool parts and pretend the CO2 is not bubbling up out of the water at other locations. We could also ignore all the pollutants dumped into the water along with the CO2. Yes, the main plan for putting the CO2 in the ocean is to take the smoke from industrial processes and pump it under the ocean where nobody can measure any of the pollutants and poisons going into the water from the smoke. Dumping the poisons in the ocean is the real reason for pumping smoke into the ocean.
There is also the occasional plan to extract CO2 from the atmosphere and pump the CO2 into the ocean. You have to burn oil or coal to produce the energy to extract the CO2 and you extract less CO2 than you produce. What a stupid idea.
If you use a clean power source to extract CO2, you get better results by using the clean power source to replace the oil and coal creating the CO2.
Pump CO2 into Mines
Find an old mine shaft. Extract CO2 from the air. Pump the CO2 into the mine shaft. Sell carbon credits for all the CO2 pumped into the mine. What a great idea for making money. You can sell the carbon credits to the companies that burn coal and oil to produce the electricity you use when you extract the CO2.
You could build an atomic power plant to provide the electricity to extract the CO2 but you would have to keep one of the mines ready to bury the radioactive waste from the power plant and, eventually, the whole power plant when the power plant wears out.
There are no air tight mines big enough to hold the amount of CO2 you would have to store to make a difference to the atmosphere. A better use of mines would be to store wood. Sequester the carbon from the atmosphere using clean energy efficient tree farms then harvest the wood and store the wood in mines. You are almost repeating the process that made coal.
Use a Chemical
There are plans to sequester carbon by mixing CO2 with chemicals that lock CO2 into a solid form. Calcium carbonate is the common mineral we see as limestone, marble, chalk, and is the main ingredient in bones. You can manufacture calcium carbonate by combining CO2 with calcium oxide, commonly known as lime. You can then bury the calcium carbonate to bury the CO2 or you can use the calcium carbonate as plaster and as a filler for plastic.
How to you manufacture lime? You heat calcium carbonate to release the CO2. Yes, to store a ton of CO2 using lime, you first release a ton of CO2 to make the lime. Along the way you need a lot of heat which means you burn fossil fuel and release more CO2.
You could grow fish and crustaceans, dry their bones and shells, and bury the bones and shells. This is the way limestone is formed at the bottom of the ocean. The calcium for the bones would come from calcium in the water and the calcium in the water is from calcium leached from limestone, a process that releases CO2.
The only chemical that looks like a winner for storing carbon is cellulose and that is manufactured by plants. Buy wooden furniture instead of plastic.
You can offset your carbon usage by paying somebody to plant a tree. 3.7 tons of CO2 contains one ton of carbon. To store one ton of carbon in a tree, you need two tons of tree. If a tree weighs 10 tons, it stores 5 tons of carbon and has removed 18.5 tons of CO2 from the atmosphere.
Our annual production of CO2 is 25 tons. To get rid of 25 tons of CO2, we have to store 6.75 tons of carbon in a tree weighing 13.5 tons.
One hectare of medium quality land can produce 250 tons of useful timber over 20 years. 250 tons of wood is 125 tons of carbon which is 462.5 tons of CO2 removed from the atmosphere. 462.5 tons of CO2 is 18.5 years of your production. You need slightly more than a hectare of land to offset your CO2 production.
A hectare produces more than 250 tons of plant material but the remainder of the plant material is burnt or recycled as compost and ends up back into the atmosphere. You would start your hectare of trees by planting 1100 trees then thinning out the trees every few years to produce space for the remaining trees. The final crop of trees would be around 200. Most of the material removed during thinning will end up as a temporary carbon store, not long term.
At the end of 20 years the trees are cropped and 250 tons of wood is used in house frames and furniture that will last many years and may be recycled for other uses. Demand wooden furniture instead of plastic furniture.
The cleared land can be planted again to produce the next crop of trees. To offset your carbon production, you would have to buy the trees every 20 years. If you are lucky and buy a share in a productive viable tree plantation, you will receive money from the sale of the first crop and that money might be enough to pay for the planting of the next crop.
Leucaena is a fast growing plant used to feed cattle and now promoted for carbon sequestration with the suggestion that Leucaena is the fastest plant for capturing carbon. They do not point out that the plant is small, compared to trees, and will never capture the amount of carbon a tree can capture. Leucaena is short lived and returns all the carbon to the atmosphere when the plant dies. That makes Leucaena a temporary way to remove a little CO2 but not a way to lock the CO2 out of the atmosphere.
Australia is famous for our Eucalyptus trees and now the trees are grown in dozens of countries world wide. Many countries use the trees to sequester carbon. People in Australia buy carbon credits from foreigners who use some of the money to plant Eucalypts overseas when we could plant them ourselves. The money going overseas weakens the Australian economy, leading to more farmers going broke. We could pay the farmers to plant the trees here, which would help farmers feed their families, and provide local timber to replace expensive imported wood, further strengthening our economy.
Eucalypts are flammable because of a high oil content in their leaves. Watch the bush fires that destroy the suburbs around Los Angeles. A major cause of the sudden huge fires is the Eucalyptus tree population, one in every back yard and many more growing as weeds in all the canyons. Americans imported the tree from Australia but not the fire fighting techniques required to manage the tree.
Eucalypts have one advantage in the warm dry bushfire areas of Australia. Eucalyptus leaves burn fast, so fast that the tree crowns explode, but the rest of the tree often remains without burning then begins growing again after the next rain. The bulk of the carbon remains sequestered in the living tree.
Eucalypts can store massive amounts of carbon if planted in an area free from fire. Eucalypt wood is a hardwood that is great for solid structures and can be used instead of steel in buildings up to several stories high. Once completely dry, the Eucalypt wood can be so dense that it resists fire for a long time. Many old Australian warehouses have Eucalypt frames and some have survived several fires without structural damage. By comparison, steel frames become weak at low temperatures and collapse, bring down the whole building. Eucalyptus wood is a great building material and those buildings can store the carbon in the wood for hundreds of years.
A Eucalypt hardwood frame uses little energy for initial processing and sequesters massive amounts of carbon. The alternative frames of steel and concrete both use massive amounts of energy to create the steel and concrete. When you build with Eucalypt instead of steel, you reduce CO2 in the atmosphere instead of increasing the CO2.
Grevillea Robusta or Silky Oak is an example of a rarely grown timber of greater value than the common plantation timbers. The wood is more valuable and is perfect for highlights on furniture. There are a small number of plantations that will supply more wood which means the price may drop but it is also a wood that could come into fashion if there was a steady supply of quality mature timber with an even grain.
There are lots of potential plantation trees with long term value for quality furniture that will be used for many years. While none of them may store a lot of carbon, you could store a massive amount of carbon by setting up many plantations for every species. When they are subsidised by carbon credits, you do not have to make a commercial profit from every species. All you need is some sort of long term use for the varieties of wood that are not picked up for furniture or construction.
Less interesting varieties of wood might come from trees that grow in ecological niches that are not suitable for regular trees. You might plant mangroves in muddy salty soil. You do need an eventual use for the wood so that the wood does not recycle into CO2. Mangrove wood might turn out to be suitable for cardboard or as a filler in wood laminates. When we plant trees, we need to look at unproductive areas of land so we do not reduce food production and exotic species can fill those unproductive areas.
Some varieties of pine tree can grow close to the ocean, some survive in areas too cold for Eucalypts, and some pines have wood useful for building. Pine can sequester carbon by locking up the carbon in wood used for building but pine is useful mainly for smaller buildings and wall elements within buildings based on frames of stronger wood. You still need the Eucalypts, or equivalent hardwood, for the major structural elements.
Pine tree plantations are common in Australia and they burn rapidly in the warn dry Australian climate. When you plant pine trees in Australia to sequester carbon, you have to allow for the massive number of trees that will burn to the ground, releasing all their carbon into the atmosphere. None of the trees survive and you have to start right back at the beginning. Most plantations will survive and we can create extra plantations to allow for the losses.
Use pine trees in climates too cold for Eucalypts.
You can plant beans then process the beans to produce oil to replace diesel fuel. Soya bean is grown worldwide and contains too much fat compared to protein, resulting in obesity. During the processing of soya bean for affluent countries, extract at least half of the fat to make the beans acceptable as a food source. The extracted fat is oil you can convert to biofuel to replace diesel fuel, reducing CO2 production.
Hemp is the main product from Cannabis sativa. Products produced from hemp include rope, string, canvas, and clothes. The same products are produced from fossil oil by the massive petrochemical industry. When the plastics break down, they release CO2 into the atmosphere. The plastic you buy today will slowly release CO2 for a hundred or more years.
If we reverted to hemp, the CO2 released into the atmosphere by hemp would be CO2 removed from the atmosphere by hemp, a completely natural cycle. To replace some plastic products, hemp would require waterproofing and we can do that using modern oils and waxes extracted from plants.
Hemp can be used as part of building materials to replace foam plastic. Help does burn but not as fast as plastic foam and does not produce the toxic fumes you get from hot plastic.
Rapeseed, Brassica napus, is grown worldwide to produce food and oil. The plant is related to broccoli, cabbage, mustard, and turnip. Some people harvest the plant as a green vegetable just before the plant flowers. The seeds contain oil that is useful as a lubricant and could be used to produce biofuel. After you extract the oil from the seeds, the remaining material is used as a high protein feed for cattle.
Cars produce huge amounts of carbon released into the atmosphere by the heat in the engine plus the biological breakdown of the used oil. You can recycle the oil and the recycling produces more CO2. Rapeseed oil could be used to replace fossil oil in car engines if the engines were changed slightly to work with rapeseed oil. Car engine oil would then be a gigantic storehouse of carbon sequestered from the air by plants.
Stop tilling the Soil
Some whackos really believe you can reverse out a hundred years of massive fossil fuel burning by a minor change to agricultural practices. Tilling the soil, ploughing, turning over, hoeing, kills weeds by turning the soil upside down and the dead weeds degrade, releasing CO2. The ratbags talk about doing away with tilling to stop the release of CO2. They would spray the weeds with herbicides instead of tilling. Would this stupid idea make any difference?
The bulk of the carbon held under the soil is in tree roots, not weed roots. When weeds die, they release CO2 no matter how they die, by tilling or by herbicide. Both tilling and herbicide spraying require fuel to run the tractors pulling the sprayers or tillers. In regular soil, there is very little CO2 difference between tilling and herbicide based weed management. In hard soil the tilling process uses heaps of fuel to break up the soil and there could be an advantage from the use of herbicides but it is not in the amount of carbon retained in the soil, it is only in the carbon burnt to power the tractors.
Herbicide usage is promoted by the same petrochemical industry that promote plastics over natural materials. If you really want to do away with tilling and not promote massive use of petrochemicals as a substitute, switch to farming trees including food trees such as apples, almonds, and walnuts.
Breed conventional food plants to be perennials instead of annuals. As an example, some chilli plants crop for several years and you can replace annual basil plants with perennial basil. If all plants lasted 5 years instead of one, you would till the soil only one year out of 5 instead of every year.
Mulch keeps weeds down and feeds plants. Mulch is a great replacement for herbicides when you grow plants that last longer than a year. You save money because you lay the mulch just once instead of spray, fertilise, spray, fertilise, spray...
Replacing tilling with better land management practices does temporarily retain extra carbon but the result is closer to reversing back couple of years instead of a hundred years. The real saving is in reducing future fossil fuel usage by reducing the number of times you drive the tractor over the land.
Farmers use fossil fuel to power their tractors, harvesters, milking machines, and everything else. They also have wind blowing over their land. If the wind is strong and regular, the farmers can use wind power to create electricity for their milking machines and other local needs. The excess can go out onto the electricity grid to replace fossil fuel equivalent to the fuel used in their tractors. Wind power could make some farmers carbon neutral before they count the contribution of their crops.
If a farmer can make enough money selling electricity from wind power, the farmer can then devote more land to trees to sequester significant amounts of carbon.
Lots of farms have patches of bare rocky ground that contains no plants. If there is no wind blowing over the barren areas, the areas could be covered with solar panels to capture the sunlight as electrical energy. The electricity then replaces fossil fuel usage to make a farm carbon neutral before the crops appear. Like wind power, solar power frees the farmer to switch some land to trees to sequester carbon.
The best way to sequester carbon is using plants but just planting trees is not enough, we have to replace fossil fuels with plant extracts, wind power, and solar power. The wood from trees has to be used in ways that store the carbon instead of releasing the carbon back into the environment.