Agriculture in a Zero Emission Society

Whilst renewable energy will play a significant role in replacing fossil fuels it cannot replace them entirely. To achieve a zero emissions future the World needs to reduce and be more efficient in the way it uses all energy. Similarly heavy industry such as steel cannot run on renewable energy and whilst carbon capture technology could remove and store CO2, it’s not a solution to all our fossil fuel emissions.

Where fossil fuels cannot be replaced by renewable energy or the CO2 captured and stored, offsets, (mitigation strategies to sequester carbon equivalent to the emissions) could be utilized so that the net effect is zero. Since all the reforestation and afforestation strategies are needed to capture historical CO2 emissions [cant see the woods for the trees ], offset for future fossil fuel burning must look to exploit other measures to sequester carbon, most of which lie within land use and agricultural practices.

Note: The figures below are all approximations that have been derived from easily available data on the internet; data which is itself little more than guess work. The purpose is therefore not to provide quantitative analysis but a qualitative summary; to encapsulate the scale of the problem we face and the potential of a given action to contribute to the solution. Only then we can truly quantify a system.

Soils as Carbon Sinks

Compost, green manure, bio-chars and zero till have all been widely suggested as means for agriculture to mitigate CO2 into soils. Whilst changes in land use and management result in changes in the soils carbon content, climate, soil texture, hydrology and depth are also significant factors in a soils capacity to sequester carbon. Tillage, particularly excessive tillage causes soils to lose carbon and as a general rule the less disturbance a soil has the greater the capacity to store carbon. Thus the greatest natural stores of soil carbon are to be found in the undisturbed soils of forests and grassland, whereas the lowest content is to be found on cultivated. It is within the cultivated soils, 1.5billion ha (11% of the Earths surface) that the capacity to act as carbon sinks chiefly lies.

Compost

Compost has a number of significant benefits when used in agriculture [compost science] and can indirectly lower emissions by improving soil structure and reducing tractor fuel consumption, and by improving nutrient cycling and reducing fertiliser inputs. However as a means to sequester carbon it’s benefits may be minimal.

Microbial action on the compost, action that is responsible for improving the soil structure and the nutrient cycling is similarly using the compost as an energy source and is respiring in the process. The natural process by which microbes breaks down the organic matter, releasing the nutrients also releases the carbon as CO2 back into the atmosphere. The process follows a first order kinetics curve where 50% remains after three years, 25% after six, 12% after twelve 6% after twenty five and 3% after fifty years. Whilst crude approximations the general rule for compost added at regular intervals (1-3 years) is that it achieves a net balance of soil organic carbon after 50 years. Further additions simply maintain that level.

For an agricultural mineral soil SOC cannot be raised above 10%, but with the current global average likely being as low as 4% there lies a potential to increase soil carbon through compost additions. As a tool to sequester carbon, compost could potentially sink 135 billion tons of carbon over a 50 year period and raise mean SOC levels to 10%. Equivalent to 2.7 billion tons of carbon a year. It would though require 135 billion tons of compost; equivalent to 19 tons per person. It is therefore an unrealistic figure and would likely still be being ambitious with a target of 7.2 billion tons (one ton for each of us). As a target it would similarly offset less than ½ billion tons of Carbon emissions a year. So whilst compost is an important component in achieving sustainability in agriculture and can indirectly reduce farm emissions it is not a means to directly offset fossil fuel emissions from other industries.

Chars (Biochar and Charcoal)

Unlike compost, chars (biochar and charcoal)  can be made from any carbon containing material including animal carcasses and plastics. Produced by pyrolysis (heating the material in a reduced oxygen environment) the carbon is converted to a more inert mineral like substrate that does not particularly interact with the soil matrix. Behaving more like aggregate(stone) Chars are highly resistant to microbial action and can remain unchanged for a 100 years or more. Chars do not in themselves contain or contribute any nutrients but with properties similar to vermiculite chars can improve soil structure, influence nutrient cycling, soil acidity and soil hydrology. Chars can likely be added to match or exceed the soils natural carbon balance without affecting the soils ability to function and may actually improve it. This gives a theoretical offset value of at least 100 billion tons of carbon as char into the worlds cultivated soils.

Chars could also be incorporated into soil prior to afforested. With the World needing to create at least 10 million ha of new woodland every year for the next 30 years as much as 7 billion tons, a quarter of a billion a year of carbon as chars could be added to soils prior to planting woodland.

Precisely where the World gets 100 billion tons plus of char from without chopping down a rain forest is another matter but as a one time means to sequester carbon and offset emissions whilst we build the renewable replacements, Chars offer great potential. However put into context 100 billion tons of carbon is the amount of emissions produced from fossil fuels over the last three years; so we need to hurry up with building the replacements.

Green Manure

More a mechanism for improving soil structure and reducing nutrient losses through better cycling green manuring adds some carbon to the soil. However the carbon is not resistant and is subsequently liberated through microbial action. As with the fuel savings and nutrient cycling of compost, green manures provide similar benefits which ultimately reduce the gross CO2 emissions of a farm unit but does not in itself sequester significant amounts of carbon.

Zero Till

As much a political argument as an environmental, zero till as a management strategy can sequester carbon. However its a strategy that cannot be used in conjunction with compost and green manures and so relies on higher fertiliser and herbicide use. This results in increased N2O emissions which largely cancel out the benefits of the carbon sequestered. So whilst there may be other benefits to zero till, such as fuel savings there is likely very little gain from the carbon sequestrated.

Wetland Restoration and Creation

Wetlands cover 6% of the world’s surface, approximately 700 million ha. Half of these wetlands are peat bogs and peat lands that have twice the carbon sequestration potential of forests. During the 20th Century the World has lost over 64%of it’s wetlands, some 1200 million ha, an area larger than Canada and 5 times the area of tropical rain forest deforestation over the same period.

Restoring these wetlands could prove easier and sequester twice the carbon that would be sequestered by afforesting the same area. With Europe having lost 66% of it’s wetlands over the last 100 years and the USA 53% since the 1600 there lies the potential to sequester several hundred million tons of carbon in restoring North America and Europe’s wetlands. The global potential could well be in excess of 2000 million tons of carbon. It is worth bearing in mind that the conditions which led to the formation of fossil fuels in the first place, particularly coal, was a planet dominated by swamp forests. The carbon we have released over the last 100 years was originally captured and stored by the wetlands of the carboniferous period.

In addition to restoration creating new bogs, swamps salt marshes and coastal lagoons could further sequester large amounts of carbon, create habitat and provide coastal and flood protection from future sea level rises.

Biomass and Bio-gas

Biomass be it wood, straw or cow dung when burned produces GHG emissions. Those emissions may not be from fossil fuels but they are emissions non the less. Whilst research suggest that over the long term biomass results in net zero emissions, in the short term they may actually add to the problem.
Biomass fuels are also controversial since they require re-purposing of crops and cropland to grow the biomass. For every ha of biomass grown a ha of food land is not. Furthermore biomass used for fuel is biomass that cannot be used for char manufacture and as chars offer some offset value any diversion of biomass to energy production impacts on that potential.

Biogas, where manures and other organic wastes are used in anaerobic digesters to produce methane has the potential to reduce the reliance on fossil fuels but not GHG emissions. Biogas does not reduce emissions, it replaces fossil fuels with methane, it similarly relies on passive uptake to offset those emissions and thus maintains the net emissions total. Unless carbon capture technology is subsequently applied this gives only an efficiency gain, one that to make the manure ‘mineable’ requires animals to be intensively reared in sheds.

Bio-diesel: Tree Bourne Oil Seed

Bio-diesel can be made from any oil bearing seed including crop plants such as sunflower or maize or from high oil bearing non-edible species such as Jatropha. However as with biomass the re-purposing of crops and lands to produce bio-diesel is controversial. Jatropha, and other shrub and tree bourne oil seeds (TBO’s) could however be grown as hedgerow without compromising crop lands.

Grown as hedgerow TBO’s would further provide carbon sequestration, erosion protection and habitat creation whilst having minimal impact on the lands ability to produce crops. This is not so much an offset but a true net zero emission replacement for fossil-fuels: the oil being a commercial component in a hedge that sequesters carbon, prevents soil erosion and provides habitat.

Such a system could even grow bio-diesel for another industry such as International shipping which emits 0.6 billion tonnes of CO2 (1.74% of global emissions) per year from burning 0.2 billion tonnes of heavy fuel oil [fossil fuels result in 3.15 times CO2 when burned]  Switching to or blending bio-diesel with heavy fuel oil would directly reduce fossil fuel emissions.

However to grow sufficient Jatropha to supply the current international shipping with 0.2 billion tonnes of bio-diesel would require 35 million ha of land (2.3% of cultivated land), an area the size of Germany.

International aviation, which similarly contributes 0.5 billion tons of CO2 using a slightly more refined fuel (kerosene) than Heavy Fuel oil could also potentially switch to bio-diesel. Aviation fuel (kerosene) has a lower wax content to prevent it solidifying at altitude (low temperature) whereas organic oils tend to solidify. If a bio diesel that can remain liquid at low temperatures could be found it potentially replace aviation fuel but as with shipping it would require an area of land covering 28 million ha, 1.8% of cultivated land, to grow it.

To grow a replacement fuel for shipping and aviation an area the size of Germany and Poland combined would be required. However as hedgerow in the tropics TBO’s could contribute to reducing shipping’s consumption of fossil fuels by as much as 10%, the other 90% will have to rely on renewable energy.  New Golden Age for Sailing Ships?

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With all reforestation and afforestation projects for the next 100 years set aside to capture historical carbon, only chars and wetland restoration remain as strategies that offer any significant opportunities for carbon offsets on agricultural land. Whilst only bio diesel, derived from non crop plants on non crop land, can be considered a renewable bio-fuel with the potential to replace some fossil fuel use. Biomass production, it’s larger more comprehensive cousin competes with both food and forest crops for land and with Chars for raw material. We cannot both burn our waste wood and char it. Similarly whilst bio-gas makes an efficient use of methane emissions it converts those emissions to CO2. So whilst biogas extracts some energy from GHG’s on route to the atmosphere it is not an offset nor a replacement but just a slower path to the same climate catastrophe.

The use of compost, green manures and reduced or conservation tillage practices whilst in themselves do not sequester significant quantities of long term carbon, when part of a comprehensive management strategy such practices can have positive impacts on fuel consumption and fertilizer use and thus reduce the overall carbon footprint.

Agricultural Emissions

ghg-emissions-by-sectorAgriculture is itself a major source of GHG emissions and whilst forestry is the largest contributor, land, crop, livestock and management practices all contribute to GHG emissions. These too need to be mitigated and offset.

Agricultural machinery, processing and transportation of goods are all major contributors to the carbon footprint of an agricultural enterprise and it’s produce. The emissions from a farm are though complex, some such as fuel and fertilizer use can be aggregated and crude approximations on how the emissions distribute according to crop and land can be made.

However the mechanisms by which emissions specifically accumulate onto goods within the farm and as those goods pass through subsequent supply chains is not transparent. So whilst figures may be accurate at the national and international level they may not reflect what is actually happening within different units. This has the consequence of shifting responsibility onto the whole industry, masking the extent higher emitters contribute and failing to acknowledge the efforts of low.
dfm-where-the-data-comes-fromSo whilst it is possible to calculate global fossil fuel production, and to approximate the net emissions resulting from those fuels by country and per capita [the global carbon footprint]; and to further break this down by industry, it is difficult to extract meaningful information to differentiate between high and low emitters within those industries. What is therefore needed is a mechanism, a framework that allows all the data to be quantified to reflect the true carbon footprint of any enterprise or goods at any scale and relevant to the whole. A framework such as DFM.

 

The Global Carbon Footprint

Fossil Fuels 

Since 1751 approximately 392 billion metric tonnes of carbon have been released to the atmosphere from the consumption of fossil fuels and cement production. Half of these fossil-fuel CO2 emissions have occurred since the mid 1980s.[Carbon dioxide information analysis centre]

carbon-footprint-globeIt’s widely reported that the World emitted another 38.2 billion tonnes of CO2 in 2015, an 8% increase on 2014’s 35.6 billion tonnes, raising the global average of CO2 from fossil fuel burning to 5.3 tonnes per person and adding another 10% to the 392 billion tonnes released over the last 200 years.

In 2014 the top five CO2 emitting nations, responsible for 2/3rds of all fossil fuel carbon emissions, were China (10.5bt), USA (5.3bt), European Union (3.4bt), India (2.3bt) and Russia (1.7bt).

Whilst five of the biggest emitters relative to population were Gulf states: Qatar (39.13t), Kuwait (28.33t), United Arab Emirates (21.3t) Oman (18.92t) and Saudi Arabia (16.8t).

Australia (17.3t), The USA (16.5t) and Canada (15.9t) came next whilst Kazakhstan (14.2t) and Russia (12.4t) came 9th and 10th in per capita emissions.

China in 20th (7.6t) whilst the European Union, which came 23rd (6.7t) carried some big emitters such as the Netherlands (9.4t), Germany (9.3t), Belgium (8.7t) and Poland (7.8t). Only Spain and France’s emissions matched the global average of 5 ton. India, the 4th largest emitter by country, produced only 1.8t per head putting it in 42nd place, 5th from bottom and beaten only by Indonesia, Philippines, Pakistan and Nigeria. [wikipedia]

carbon-footprint

So whilst the industrialised nations are the principal emitters of CO2 from fossil fuels, the residents of the Gulf states have a bigger carbon footprint than any other geographical region. Qataris in particular have 2½ times the carbon footprint of American’s and 43 times that of Pakistanis.

Land Use and Managementgreenhouse-gas-dfm

Land use changes, in particular deforestation, where 2/3rd’s occurs to supply just five global commodities [cant see the woods for the trees], contributes a further 6.5 billion tonnes (11%) to global GHG emissions. Methane from livestock contributes a further 16% whilst Nitrous Oxide from fertilizer use contributes another 6%. [EPA]

So whilst fossil fuel burning (65%) remains the main contributor to GHG emissions, land use changes and management practices are responsible for 33% of global GHG emissions. When added together, fossil fuels and land use GHG emissions raise the average global carbon footprint to 7 ton per person per year.

The Paris Agreement: 20/20 vision

If global emissions continue to increase at 7% per year, as developing nations catch up on the industrialized; then by 2020, when most nations expect to start implementing the Paris agreement, global emissions will be at 65 billion tons a year and global per capita footprints at 8.5t per person. We will have added another 250 billion tons of carbon to the atmosphere pushing the planet towards if not over the long term temperature goal of Article 2:

holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels,

Article 4 of the Paris agreement states that “In order to achieve the long-term temperature goal set out in Article 2, Parties aim to reach global peaking of greenhouse gas emissions as soon as possible.” However even if the World went on to reduce it’s net emissions to zero by 2050, it will have added a further 900 billion tons of CO2 to the atmosphere in the process: sufficient to double atmospheric concentrations and cause a mean global temperature rise of 3-6 degrees Celsius by the end of the century. Such a scenario would lead to accelerated melting of the Worlds glaciers and cause a global sea level rise in the tens of metres. It is similarly, based on the evidence to date, the most likely scenario.

To avoid catastrophic climate change the World must significantly reduce the use of fossil fuels with immediate effect. It must develop and deploy, on a grand scale, alternative renewable solutions (wind, solar, water, biomass) and it must actively restore the tropical forests lost since 1990. It must further increase global forest extent by at least another 10% and it must continue to do so for the rest of this century and beyond.

It must do this because it did not act to arrest the problem 30 years ago and if it waits another 30 it will be too late.. Admittedly climate was not on the international agenda but deforestation, habitat loss and species extinction were [Our Common Future 1987]. Despite the warnings of the Bruntland report and the the subsequent 1992 Rio Declaration from Earth Summit I, over a third of global deforestation has occurred during this period and the World is on the brink of the biggest extinction event since the dinosaurs. What to do?

A 75% reduction in fossil fuel use

If we cut our current fossil fuel emissions (38.2 billion tons CO2) to reach a net emissions target of 10 billion tons CO2 by 2030: a global carbon footprint of < 1.5t per capita. This would result in the emission of 200 billion tons of CO2, and we might meet the Paris agreement threshold of 2 degrees C. If we take till 2040 to reach the baseline of 10 billion tons then 350 billion tons of CO2 emissions will result and we will likely miss the 2 degree threshold. Wait till 2050 however and 500 billion tons of CO2 emissions will occur, we will not be able to keep global mean temperate increase below 2 degrees C and in all probability it will have already reached and exceeded that by 2050. We will still need strategies to mitigate the 10 billion tons we produce as a base line as well as the 400 billion historical emissions but the longer we delay, the more difficult and painful it will become.

co2-emissions-75-percent-reduction

Deforestation and Agriculture

The EPA estimate that one third of GHG emissions originate from agriculture; 6 billion tons as CO2 (11% GHG emission), whilst methane from livestock production contributes another 16%(UNFAO estimate 14.5%) and Nitrous Oxide from fertilizer use 6%. In total Agriculture contributes the equivalent of 18 billion tons of CO2 per year to GHG emissions.post-paris-co2

The largest single cause of CO2 emissions is tropical forest deforestation. The UNFAO estimates that in the last 27 years 1.29 million km2 of forest, an area equivalent to France, Spain and Portugal combined, has been lost. Much of this forest has been felled to grow soybean, palm oil and beef to supply global markets.

An end to deforestation would thus dramatically reduce the CO2 contribution of Agriculture bringing it down to or even below a billion tons per year. A 50% reduction in the beef and dairy industries would similarly reduce  agricultural GHG emissions by another 8%.

Together with reducing Fossil fuel emissions to 10 billion tons these measures would bring global GHG emissions to under 25 billion tons. We would still be adding to atmospheric concentrations of GHG’s, but at half the rate we are now, so still sufficient to maintain our course towards a climate catastrophe. A catastrophe we cannot avoid until we reduce our net emissions to zero and take steps to recapture and store the 400 billion tons of historical carbon emissions.

Reforestation and Afforestation

To recover the 129 million hectares of forest lost since 1990 in the same number of years would require planting a new forest the size of Switzerland every year for the next thirty. A forest that would, in 100 years, recapture most of the carbon emission from the original deforestation (200 billion tons).

Afforestation, the creation of new forests on agricultural and other land would also capture some of the carbon emissions derived from the burning of fossil fuels during the same period. However as afforestation is not as effective as reforestation a plantation of 260 million hectares, the size of the Kazakhstan, would be requires to capture the same 200 billion tons of CO2.

Over a 100 year period these two forests projects, which collectively would cover an area the size of India and Pakistan, would recapture the 400 billion tons of historical CO2 emissions. world-map

However even with these massive mitigation projects in place, a 75% reduction in fossil fuel emissions and a 50% reduction in methane emissions (an outcome that requires 50% of the World that is not vegetarian to become so) by 2030, the World will still go on to produce 1.5 trillion tons of GHG emissions during the 21st Century.

This is the reality of our 21st Century Global Carbon Footprint.

Climate Catastrophe Time Line

2030…. The World has cut its fossil-fuel emissions by 75% to 10 billion tons a year. Similarly 50% of the World’s meat eaters have become vegetarian and we have stopped all deforestation and bought all commercial forests into zero carbon management: our emissions are down to 20 billion tons a year…

forests-carbon01We will have reforested enough of the tropics to cover Portugal and the Spanish region of Galicia  and similarly planted new forests across the World’s other regions which would collectively cover Germany. However none are established sufficiently to make any significant contribution to mitigation, so the global temperature is still rising and we are, despite these efforts, 50% worse off than when we started: we now have 600 billion tons of carbon in the atmosphere to deal with and are adding another 20 billion every year.

forests-carbon02

 

2040…  The tropical forests  have expanded and now cover the plains of Spain whilst the new forests has grown to cover an area encompassing Germany and Poland. The good news is the earlier forests are now capturing carbon: perhaps 10%, so 4 billion tons of the 40 billion they will eventually capture. The bad news is global emissions now top 800 billion tons.

forests-carbon03

 

2050… Despite having now reforested the tropics with sufficient wood to cover Portugal and Spain, we are but halfway there, there is still the equivalent of France to plant before we recover what was lost in the last two decades of the 20th century. Similarly the new forests now cover an area that swallows the Czech Republic, Slovenia, Hungary and Austria. As with the tropical forest we are still not there, there is still Belarus, Ukraine and Romania to plant.

If our fossil fuel emissions are still at 10 billion tons a year then another 100 billion tons of CO2 will have been added to the 800 billion already in the atmosphere. If meat eaters are still insisting they would rather eat their bacon than save it, then they will have similarly added another 100 billion tons in the form of methane. On the plus side the first of the forests will likely have captured 25% (10 billion tons) of their carbon potential and the second 10% ( 4 billion tons), so our efforts may have been sufficient to keep the total global carbon emissions from fossil fuel burning and deforestation below the one trillion tons mark but by 2099 another 500 billion tons of GHG’s will have been added to the atmosphere.

carbon-footprint-globe

 The End of the Fossil Fuel age

However; if  on reaching 2030 the World has achieved a 75% reduction in fossil fuel emissions,  adopts a zero emissions target for the next ten years, and similarly a vegetarian diet, then by 2040 the fossil fuel age will come to an end leaving a 700 billion ton carbon footprint on the atmosphere. As long as the World continues with the reforestation and afforestation programs then by the end of the 21st century this could be down to 400 billion tons.. but then pigs might fly