Back in 2005 we published the feature “Jatropha in Africa – Fighting the Desert & Creating Wealth.” About two years later we rewrote the editor’s introduction to this story, stating, among other things “the yields claimed in this story have been challenged by many of our readers, and the author may have been optimistic.” Today yet another reader challenged the yields noted in our feature. Their comments – coming from someone with operating experience in Madagascar – add useful data to the ongoing question as to the economic and ecological sustainability of first generation biofuels:
“Dear Sir: Your suggestion that Jatropha curcas could make an ‘incredible contribution to economic development in Africa’ overlooks a number of important points. Assuming your seed/ oil yield claims are achievable, it would require a harvest of about 400 million tonnes of seed to deliver the volume of oil you refer to. Under most circumstances, Jatropha curcas produces one crop per year with a maximum harvest window of about 12 weeks. Currently, hand harvesting is the only practical option. An average worker can pick and shell 10 – 15 kilograms of seed by hand per day. If you assume 6 working days per week, the maximum harvest ‘potential’ per worker is 1 tonne of seed per season. So you would require 400 million people hand picking Jatropha curcas seed to meet your objective. In reality, suggestions of seed yields of 8 tonnes per hectare and 30% oil content are extravagent in the extreme. We are growing Jatropha curcas commercially in Madagascar. We are seeing average oil contents in the range 25 – 27% of which 20 – 22% is recoverable by mechanical expression. In a well managed plantation setting, we expect that yields in excess of 200 pods per tree are unlikely. This equates to about 1 tonne per hectare at a population density of 2,500 trees per hectare. We anticipate seedling trees would need to be 7 years old to achieve this yield level. We are averaging about 60 pods per tree/ 300 kg per hectare from 5 year old trees this year. Yield from our 4 year old seedling trees was neglegible ( aprox 3.3 kg per hectare ) in 2007. We initially approached the production of Jatropha curcas with great enthusiasm but now have grave doubts as to the commercial viability of the exercise. Certainly, it is unrealistic to suggest tying up vast areas of African land for 4 non productive years and finish up with a crop that will eventually provide a maximum of 3 months productive work with very meager returns to a participating farmer. At least this is our opinion based on practical experience rather than media hype.”
Taking the best case figures referenced here, mature Jatropha curcas trees will yield one ton per hectare per year, and about 25% of this tonnage can be extracted as oil. Since there are roughly 7.3 barrels of oil per ton, and 259 hectares per square mile, then mature Jatropha curcas trees will yield 473 barrels of oil per square mile per year. This is one of the lowest yields we’ve ever heard of – but this is from someone on the ground.
Another interesting point made by the writer is the labor required to harvest meaningful amounts of Jatropha oil. Amidst our belated awakening to the environmental and climatological havoc wreaked by deforestation to make way for biofuel plantations in the tropics, as well as growing realization first generation biofuel will not make much of contribution to total global energy production, is a lingering unawareness of the human cost. Biofuel may or may not bring economic benefits to the tropics, but how the workers on these plantations are being treated is a completely separate issue that deserves far more attention.
Returning to yields, as we reported in “Biofuel’s Potential,” if you are able to get biofuel yields up to 10x what is currently our best case – from 5,000+ barrels per square mile per year to 50,000+ barrels per square mile per year, then all the petroleum currently used each year worldwide could be grown in an area of only about 650,000 square miles. That is only about 6% of the arable farmland in the world. But is this honest math based on realistic estimates?
According to our writer, 500 barrels per square mile per year is their reality – for a crop we have believed to be one of the most promising first generation biofuel feedstocks in the world. At a yield of 500 barrels per square mile per year, it would take 65 million square miles to replace 100% of the petroleum used each year worldwide – and the entire land surface of the planet is only 56 million square miles.
What is the overall yield today, on average, for first generation biofuel crops? We know sugar cane in Brazil can yield over 5,000 BBLs per square mile per year, as can oil palms in Indonesia. But corn in Iowa only comes in around 2,500 BBLs per square mile per year, and apparently, Jatropha in Madagascar is only delivering about 500.