Biology Comics

Biochar and Silicate Rocks

Heavy rains are increasing, Arctic ice is melting, Russian peat bogs are burning, methane is bubbling out of the East Siberian Sea, the summer’s heat and humidity grows and grows. Alone each means nothing, together they add up to a changing climate, which only demagogs and idiots ignore.

Of course it may all turn around and (especially here in the U.S. northeast) turn cold for the next 1000 years. We are poking the climate beast, with unpredictable results, as Wallace Broecker remarks.

The problem is too much carbon dioxide (and other heat trapping gases, such as methane, nitrous oxide and the chlorofluorocarbons) in the atmosphere. And too much soot and black carbon in the air and falling out on Arctic ice.

We’re putting the gases (and the soot and dust) there. Since modern life runs on fossil fuels, we aren’t likely to stop; or stop fast enough. Is anyone going to make China stop? Or India? Or the U.S. for that matter?

Saving energy is boring, nuclear power risky, wind and solar are expensive and require storage schemes (pumped water reservoirs, chemical batteries) that are expensive, destructive or dangerous. Forget about sequestering carbon from smokestacks, it’s too complicated, it takes too much energy, it’s a pipe dream. What free lunch?

So what about continuing to dig up coal and geoengineer the planet? Launch tiny mirrors into the atmosphere to reflect sunlight back to space. (Of course the ocean and atmosphere would continue to acidify.) Spray sulfur dioxide from planes into the stratosphere to reflect sunlight, or hey!—just remove the controls on sulfur from fossil fuels. Or spray seawater into the atmosphere to increase the reflectivity of clouds. Or pump seawater onto Arctic ice to thicken it. (Why not, to the last two.)

Lime the planet to counter acid rain!

The main downside of schemes to reduce incoming sunlight is that the planet will continue to acidify. As for spraying sulfur dioxide, the sulfur dioxide will eventually fall out on the land and ocean. There are probably other downsides—changes in rainfall or airflow, changes in stratospheric chemistry or the growth rate of plants. To think all such effects are predictable is nonsense.

So what about taking carbon dioxide directly from the air. One idea is to fertilize the oceans with urea (a nitrogen fertilizer), or finely ground iron (a limiting nutrient in the sea), or by installing huge pipes to increase the transfer of nutrients from deep water (where they are common) to the sunlit surface (where they fuel algal growth). The fertilized algae on the surface divide and grow, are eaten by fish (or die), and sink as tiny corpses or fish poop to the bottom of the ocean where the carbon (taken by the algae from the air) is locked up for thousands of years. Unfortunately, fertilization schemes don’t seem to work (the carbon stored is negligible compared to the effort put into fertilization). Their other effects on the sea are also unknown.

On the other hand, our overfishing of the oceans (a natural result of unregulated capitalistic effort) is reducing them to ecosystems of algae and jellyfish, while our heavy fertilization of large continental watersheds, with the resulting dead zones of maximized algal growth at the mouths of major rivers, may be storing more carbon than we realize. (The oil in farm fertilizer producing more oil in sediments.) Of course destroying the oceans to save the planet is nuts.

What to do? Well all that boring stuff (fast breeder reactors, reducing population, cars that get 200 miles to the gallon, insulating houses, reducing poverty, empowering poor women—both the last tend to reduce population growth) helps. Reforesting or revegetating degraded lands stores carbon in soils, plants and trees. Reducing numbers of cattle and sheep on overgrazed lands (say in the U.S. Great Basin and High Plains) lets shrubs and perennial grasses store carbon in soils. So does rotational grazing of dairy cattle on eastern or midwestern pastures. Proper management of croplands lets them store some carbon (or lose less). Some writers claim the soils’ carbon stores are full after 15-30 years, but soil storage capacity undoubtedly varies with the site.


Reforesting degraded lands lets trees store carbon in their tissues and in the soil. Billions of acres of degraded lands are candidates for reforestation: much of the Mediterranean basin, including the mountainous islands; much of China; the Tibetan plateau; the Andean altiplano (both were deforested by people thousands of years ago for their crops and animals); the Himalayan foothills; much of the U.S. Southeast and Midwest; some deserts.

In the Sahel in the 1970s, millet farmers let acacia trees grow in their fields. This was a folk technique that had been mocked by modern agronomists. The trees provided forage for the animals, which meant more manure for the crops. More trees grew, sprouting in the dung of the (more numerous) grazing animals. This let the farmers raise more animals, which meant more dung and more cropland. Eventually several million acres of the Sahel were reclaimed for agriculture. The trees store carbon in the soil and have slightly increased rainfall over the northern Sahel.

The huarango tree of the Atacama Desert in Peru (one of the driest places in the world) captures water from ocean mists. Its roots draw up water from 150 feet down. It breaks the wind over the desert and, by condensing mists, moistens (slightly) the upper layers of the soil. It lives a millennium and (a mesquite) produces a sweet edible pod, which can be used for fodder, ground into flour, or made into a syrup or beer. Its fragrant blossoms support bees. The Nazca of 1500 years ago cut down huarangos to plant irrigated cotton and corn in the river valleys, exposing the desert to floods and wind erosion. Modern residents of the Atacama cut the trees for firewood. The tree is thorny, not particularly attractive, and invasive where successful and could support a life based on carbon storage, goats, honey and beer.


Agricultural revegetation of degraded lands (acacia trees, camels and millet; salicornia, a forage crop irrigable with seawater; huarango trees; jojoba, a shrub with oil bearing seeds; grapevines; mangoes; pomegranates; other fruit and nut trees) lets carbon accumulate in soils. If the prunings from the trees and the crop wastes are converted to charcoal (biochar) and spread on farmland (where the char promotes plant growth) their carbon will be stored for tens of thousands of years. (Perhaps 50,000 years: this will work in industrial agriculture; with poor peasant farmers, the charcoal will be used for cooking.)

Turning the crop residues of industrial agriculture into biochar would store billions of tons of carbon a year. Estimates range from 1-2 billion tons a year. (We release 8-9 billion tons of carbon as carbon dioxide a year to the atmosphere.) The equipment to turn corn stalks or wheat straw into charcoal is cheap, the process simple. Since biochar makes an excellent fertilizer, and reduces fertilizer runoff, the equipment would pay for itself in a year or two.

Revegetated forestlands store carbon in the trees and in the soil. The carbon in the trees is released to the atmosphere when the trees are cut (most processed trees return as carbon to the atmosphere in ten years); or when they die and decay. While growing, the forests continue to store carbon (say, for 300-2000 years). When storage slows, the best way to cut the trees is selectively, so as to expose the soil as little as possible to sunlight, which speeds up its losses of carbon. The best bottom log could be used as sawn lumber (a carbon loss, factored into any payments for carbon storage; but the trunk represents only a fraction of the tree’s mass) and the rest converted to biochar and spread back on the forest; or sold to spread on farmland. If landowners are to be paid for storing carbon, the way to maximize a forest’s carbon storage would have to be worked out; and calculated by the year or decade. We have 300 years to do that. Any payments for carbon storage should be based on real numbers, not guesses. Payments from, say, a tax on fossil fuels.

Changing agricultural practices to capture carbon; revegetating degraded lands; producing biochar involve no downsides of which I am aware. Such practices would produce a return on investment and improve the nutrient storage capacity of watersheds, and thus improve the health of riverine and ocean fisheries. We might store a quarter of the carbon dioxide we currently produce by such methods, perhaps more.

One other technique offers carbon storage, but with a limited downside. This involves capturing carbon dioxide through its natural (exothermic) reaction with magnesium oxide or calcium oxide rocks. The reaction forms stable carbonates (limestones). One can foster this reaction by mining and grinding the rocks and spreading them on land or on the sea. The energy involved in the mining and pulverizing is inconsequential in comparison with the carbon stored. Spreading the powder on the ocean (especially over the productive continental shelves) lets one reduce the acidification of the sea as well as capture carbon dioxide from the air. (A free lunch?) One picks cliffs of the appropriate rocks on a seacoast (volcanic rocks are good), sets up a mine and sends the powder down to slow moving ships that spread it over the sea. (Schemes like this have been suggested for the Scottish coast to produce builders gravel.)

In biologically appropriate situations, the mine could be made into a pit for pumped storage of seawater (another munch at lunch). This isn’t appropriate where marine life would be harmed, thus not, say, on the Palisade escarpment north of New York City, above the Hudson estuary, where the rock is appropriate and the pumped storage capacity could use the photovoltaic output of the city, but the damage to the estuary would likely be great.

The variability of solar power means it has to be backed up. The power supply for a modern grid cannot be interrupted or the system will crash. Since the output from the sun and wind is unpredictable, one must either invest in double the capacity—the fossil or nuclear fuelled grid as well as the unreliable photovoltaic or wind capacity— or have some storage that can be switched on when the solar supply falters. Flywheels; chemical batteries; compressed air in abandoned mines; pumped storage all work. Pumped water from the sea is a natural (say, on Oahu in Hawaii; in the Canaries; in California or Maine; in Scotland). A pumped storage scheme was suggested for Storm King Mountain on the Hudson in the late sixties but was abandoned after an outcry from environmentalists (me included). The high dams on the ruined rivers of the U.S. west (the Colorado, the Yellowstone, the Columbia) offer obvious sites for pumped storage: all they lack are the pumps and a safe way (for the riverine biota) to pump sufficient volumes of water back up behind the dams. (A nonbiologically invasive way to extract water from rivers would make many things better.)

Of course, the ultimate solution to climate change is fewer people, saving energy, fast breeder reactors, the electrification of transport and the energy supply (so all energy can be provided by the sun). Alleviating poverty and empowering women, the projects of the “skeptical environmentalist,” a foolish and publicity hungry Dane, will also reduce population.

Let’s do it all! Make biochar, mine silicate rocks, have one child, and plant trees.