THE MICROFARM AND CLIMATE CHANGE
Climate change is driven by increasing amounts of greenhouse gases - chiefly carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2O) in the atmosphere.
Agriculture emits lots of these gases so can be a major player in the 'what drives climate change?' story.
CO2 comes from burning fossil fuels which for farms means the manufacture and use of powered machinery, fertilizer production and application, crop, meat and milk processing, refrigeration and transport. And that includes transport to those huge distribution centres and on to those supermarket shelves in an eye-catching package with a good shelf-life.
CH4 comes a bit later in the food production process. Besides ruminants' flatulence, it comes from farm animals' excreta accumulating in tanks and lagoons where it undergoes anaerobic decomposition. It is also exhaled by the landfill hills - so nicely covered with grass - where all that packaging and cheap food thrown away decomposes, also anaerobically.
N2O comes from bacterial activity in the soil processing nitrogen-rich compounds, especially applied nitrogenous fertilizers, but also N-rich organic material like animal excreta.
The microfarmer uses little or no powered machinery, only physical exercise (as is recommended unanimously by doctors for those who desire a long and healthy life) so not much CO2 there.
With all that aerobic nutrient recycling in kraals and compost heaps and constant scavenging of what the rest of us call "rubbish", synthetic fertilizers are superfluous, so not much CO2 or CH4 or even N2O there either.
Cowpats collected from the veld - for start-up fertility
And microfarms are so small that they can be embedded in the community (check Cuba) so that fresh produce can be marketed at or near the farm gate, thus dispensing with a lot of transport, packaging and refrigeration and giving people a daily supply of fresh food. And if there is any waste here, it can conveniently be fed back to the farm animals or compost heaps. CO2 reduced again.
So far, we have only considered emissions of greenhouse gases. Can agriculture do anything to reverse their increase in the atmosphere?
This is a politician's dream and an economists' nightmare. If undertaken at power station smoke stacks, it will reduce a country's emissions at a stroke and allow all sorts of other energy-wasteful activities to continue, giving the politician happiness. But its removal from the flue gases of thermal power stations will also inflate electricity prices, and give the economist nightmares.
Nevertheless, we are overlooking two other methods of carbon capture, probably because one is so much part of "nature" - photosynthesis - and the other because we don't see it, has no smell and is free of charge - carbon sequestration in the soil as soil organic matter (SOM).
- Photosynthesis. Green plants capture solar energy and use it to convert CO2 and water to fixed energy - sugars, starch, cellulose etc, all carbon-rich. A farmer can do little to affect the efficiency of this process, but a lot to affect the quantity - by arranging for more photosynthesis to take place per square metre of land per year. He or she can extend the cropping season into the dormant season with irrigation or polytunnels and raise the rate per square metre by higher plant populations on soils of raised fertility. Actions well suited to the microfarmer.
- Increase SOM. Microfarmers are very good at this because they use vast amounts of manure, compost and mulch, while the Big Hectare Farmers apply - mainly - nitrogen fertilizer. This, too, increases SOM because of the additional biomass generated by the crops to which it is applied, but there is the risk that this added N may reduce the level of SOM where agronomic practice is poor because it can accelerate the mineralisation of SOM as well - N also being an essential nutrient for soil micro-organisms.
Of course, we are only postponing the return of this carbon to the air because SOM is always decomposing as the soil microbes 'burn' it. But the key here is that the microfarmer always tries to apply more than is 'burnt', enabling a slow nett increase in SOM to take place to a new, higher level at which there will be equilibrium. (Look at
the Classical Rothamsted Experiments on Broadbalk Field - www.rothamsted.ac.uk.)
The maths of this is interesting. Try this:
| ||A microfarmer might apply one wheelbarrow of compost or manure to 5m2 before planting it up. If there are two crops a year, this is 2 wheelbarrows or 50kg of wet material a year. Given a moisture content of 75%, this represents 12.5kg of dry matter. This, being mainly cellulose, may be about 5kg of carbon. So we are applying 5kg of carbon to 5m2 of land per year with our two wheelbarrows of muck. That is 100kg of carbon on our 100m2 garden.|
Now higher levels of organic matter in the soil will increase soil biota and their oxidising/mineralising activity; but with this constant high application rate, it is reasonable to assume that perhaps half the added carbon will add to the soil's stock, so that after five years, our 100m2 planted area will have sequestrated
100kg x 5yrs x 1/2 = 250kg.
Not bad when you add in the improvement to soil structure, fertility, water-holding capacity and permeability of the soil! And life-saving when you factor in the reduced risks of erosion and flooding
This is not something that the Big Hectare Farmers can even think about - unless they join the "No-till Revolution" which will also raise SOM levels appreciably, as well as greatly reducing fertilizer and tractor fuel use.