I recently overheard a professor in the Danish radio stating that nutrient load on the environment from organic and conventional farming is equivalent when one takes into account the lower productivity/area in organic farming. This statement provoked me to dig deeper, as I'm an avid pro ecologist. Could I be wrong...?
Nutrients
Plants form the basis for all food production. Some grow wild, and we use animals to convert them into meat/milk that we can consume. Other plants we keep, and eat either directly or feed to animals we then eat. As most of us don't shit where we eat, we encounter a problem with nutrients, especially minerals.
The plants take up minerals (I'll stick to nitrogen, phosphor and potassium here), and store them in their tissue. This bound N, P and K is transported far and wide to be consumed elsewhere, and thus deposited in a concentrated way, often at waste water treatment plants in cities, far from where they are needed by the new crops we need to eat. The Nitrogen we get rid of by de-gassing waste water (denitification), and can be absorbed by certain plants and bacteria on the fields later on. The phosphor is either accumulated in phosphate accumulating organisms, or by chemically treating the water to bind the phosphor in salts. None of these processes bind all the phosphor (5-40 % is removed according to a producer of removal equipment), and much phosphor is released into the waterways and ultimately the sea. The accumulated phosphor can either be used as fertiliser, or be dumped at landfills.
The problem with especially phosphor is that it's applied to the fields, but doesn't end up there in the end again, it ends up polluting our water. To keep plants growing on the fields we have to get new phosphor in. This phosphor usually comes from mines (especially in USA and China), and is a finite resource. This is a problem for both types of farming.
The organic farmer is not allowed to use a non-biological phosphor source, and has to rely on manure to boost phosphor content of his soil. The manure production however has the same problem as all farmers, they have to get phosphor from somewhere too - suggestions have been made to use phosphor rich seaweed to help close the loop.
Also the organic farmer can leave non-edible parts of the plant (stem, roots) to rot on the field, only removing the phosphor bound in the grains from the field, making the phosphor deficit smaller.
Because of transfer of disease the use of human faeces is often not a good solution to this problem, even though it would close the loop...
What about the carbon?
Carbon, a bit like nitrogen, transfers from us back to the crops as CO2, and is not really a concern in the discussion between conventional and organic farming. Carbon is mostly relevant as a measure of how much energy is used in the production of a given amount of food. Organic farming usually scores better here (lower carbon/food unit), mostly due to the high energy cost of producing artificial fertilisers. Otherwise the tractor of the organic farmer runs the same way the any other tractor does, and can be run on fossil or renewable fuels accordingly.
Yield.
Gross yield is higher for conventional farming. This is true for all industrial scale farming. But what's really interesting is net yield, a kind of input-output balance for farming, and that's when it gets interesting (and relevant).
I've found two long term studies, one from USA and one from Switzerland. The one from the states has run over 25 years and still going. They have equal or better yields from organic fields, with organic plots outperforming conventional during stress, e.g. drought, plant disease. Taking into account the lower cost of production (less purchased fertiliser, less pesticides and less fuel), the organic production is 20 % more profitable (when priced at the same price as conventional produce!).
The Swiss study (21 years) found that their organic plots yielded an average of 84 % of the conventional plots. But the conventional plots received 66 % more fertiliser (NH4NO3 equivs.) and used 40 % more fuel than the organic plots. This mean that the net output from the organic plots were higher than conventional plots - I'll attempt a calculation of how much by converting production and energy use into joules/ha (all numbers from Swiss report).
5.6 t/ha assuming 90 % carbohydrates, 10 % protein
2828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
5600 kg * 90 % = 5040 kg
5040 kg / 0.16214 kg/mole = 31084 moles
31084 moles * 2828 kJ/mole = 87,906 MJ (from carbohydrates, cellulose)
5600 kg * 10 % = 560 kg
5600 kg * 17000 kJ/kg = 9,520 MJ (from protein)
Total gross yield: 87906 + 9520 = 97426 MJ/ha
Energy use:
360 kg fertiliser at 28 GJ/t (source) = 10,080 MJ
570 L diesel-equiv at 35.9 MJ/L = 20,463 MJ
And some pesticide that I deem insignificant in the energy budget.
Total energy use: 10,080 + 20,463 = 30,543 MJ/ha
Net Yield:
97,426 MJ/ha - 30,543 MJ/ha = 66,883 MJ/ha
4.7 t/ha assuming 90 % carbohydrates, 10 % protein
2,828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
4,700 kg * 90 % = 4230 kg
4,230 kg / 0.16214 kg/mole = 26089 moles
26,089 moles * 2,828 kJ/mole = 73,778 MJ (from carbohydrates, cellulose)
4,700 kg * 10 % = 470 kg
470 kg * 17000 kJ/kg = 7,990 MJ (from protein)
Total gross yield: 73,778 + 7,990 = 81,768 MJ/ha
Energy use:
122 kg fertiliser at 28 GJ/t (source) = 3,416 MJ -> 0 MJ (comment on this below)
340 L diesel-equiv at 35.9 MJ/L = 12,206 MJ
No pesticides, and all organic fertiliser (manure), meaning no costly ammonia-production.
Total energy use: 0 + 12,206 = 12,206 MJ/ha
Net Yield:
81,768 MJ/ha - 12,206 MJ/ha = 69,562 MJ/ha
So with no pesticides, the net yield from the organic plots were 4 % better in the Swiss study.
I will admit that prior to me doing this calculation, I thought organic would win by more, but this just goes to show that one can easily be confused by percentages.
According to these two studies organic farming clearly comes out as the most profitable.
I know some people who would argue that I cannot simply use net joule output, as we cannot eat "diesel joules", and spending fossil fuel to create "food joules" is a net gain. This is true, but using less fuel means it'll last longer, and we don't have to replace our old tractors with new electric ones as soon, if we spend less fuel. The fossil fuels will run out.
I've found two long term studies, one from USA and one from Switzerland. The one from the states has run over 25 years and still going. They have equal or better yields from organic fields, with organic plots outperforming conventional during stress, e.g. drought, plant disease. Taking into account the lower cost of production (less purchased fertiliser, less pesticides and less fuel), the organic production is 20 % more profitable (when priced at the same price as conventional produce!).
The Swiss study (21 years) found that their organic plots yielded an average of 84 % of the conventional plots. But the conventional plots received 66 % more fertiliser (NH4NO3 equivs.) and used 40 % more fuel than the organic plots. This mean that the net output from the organic plots were higher than conventional plots - I'll attempt a calculation of how much by converting production and energy use into joules/ha (all numbers from Swiss report).
Conventional plots
Yield:5.6 t/ha assuming 90 % carbohydrates, 10 % protein
2828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
5600 kg * 90 % = 5040 kg
5040 kg / 0.16214 kg/mole = 31084 moles
31084 moles * 2828 kJ/mole = 87,906 MJ (from carbohydrates, cellulose)
5600 kg * 10 % = 560 kg
5600 kg * 17000 kJ/kg = 9,520 MJ (from protein)
Total gross yield: 87906 + 9520 = 97426 MJ/ha
Energy use:
360 kg fertiliser at 28 GJ/t (source) = 10,080 MJ
570 L diesel-equiv at 35.9 MJ/L = 20,463 MJ
And some pesticide that I deem insignificant in the energy budget.
Total energy use: 10,080 + 20,463 = 30,543 MJ/ha
Net Yield:
97,426 MJ/ha - 30,543 MJ/ha = 66,883 MJ/ha
Organic plots
Yield:4.7 t/ha assuming 90 % carbohydrates, 10 % protein
2,828 kJ/mole at 162.14g/mole for cellulose & 17 kJ/g for protein
4,700 kg * 90 % = 4230 kg
4,230 kg / 0.16214 kg/mole = 26089 moles
26,089 moles * 2,828 kJ/mole = 73,778 MJ (from carbohydrates, cellulose)
4,700 kg * 10 % = 470 kg
470 kg * 17000 kJ/kg = 7,990 MJ (from protein)
Total gross yield: 73,778 + 7,990 = 81,768 MJ/ha
Energy use:
122 kg fertiliser at 28 GJ/t (source) = 3,416 MJ -> 0 MJ (comment on this below)
340 L diesel-equiv at 35.9 MJ/L = 12,206 MJ
No pesticides, and all organic fertiliser (manure), meaning no costly ammonia-production.
Total energy use: 0 + 12,206 = 12,206 MJ/ha
Net Yield:
81,768 MJ/ha - 12,206 MJ/ha = 69,562 MJ/ha
So with no pesticides, the net yield from the organic plots were 4 % better in the Swiss study.
I will admit that prior to me doing this calculation, I thought organic would win by more, but this just goes to show that one can easily be confused by percentages.
According to these two studies organic farming clearly comes out as the most profitable.
I know some people who would argue that I cannot simply use net joule output, as we cannot eat "diesel joules", and spending fossil fuel to create "food joules" is a net gain. This is true, but using less fuel means it'll last longer, and we don't have to replace our old tractors with new electric ones as soon, if we spend less fuel. The fossil fuels will run out.
Health
With regards to the health side of things there's a lot of mixed messages out there.
A few hard facts though are:
A few hard facts though are:
- Limits for residues are often based on what we can detect, and not on whether or not it's harmful to ingest.
- Even though most conventional produce is well within the above mentioned levels, sometimes this is not the case.
- Limits for residues are set per compound and often not as a total residues value, this means that if three pesticides are present in your food, and each one is under the limit, it is approved. But studies show that pesticides can show additive effect, meaning that 1mg of "A", "B" and "C", has the same adverse effect as 3mg of either "A", "B" or "C". (suppose a limit of 2mg).
- Organic produce does not contain pesticides (other than what the wind has carried).
- Residues of pesticides severely damage ecosystems and humans - read the wiki entry on this.
- Check out this video!
Sources:
- www2.mst.dk/Udgiv/publikationer/2004/87-7614-284-1/html/helepubl.htm (Danish)
- http://www.inra.fr/en/Scientists-Students/Food-and-nutrition/All-reports/Cocktail-effects-of-toxic-substances/The-cocktail-effect-of-pesticides (Cocktail-effects)
- http://infohub.ifoam.bio/sites/default/files/page/files/misconceptions_compiled.pdf (General info)
- http://www.theguardian.com/world/2014/apr/29/french-children-farms-vineyards-exposed-dangerous-cocktail-pesticides (non-food contamination)
I might update this post as I learn more, or if I'm corrected.
As always, please leave a comment.
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