And the world's most productive ethanol crop is... oil palm
Sneak preview at our study on second generation biofuel feedstocks
A group of BioPact members have been researching the potential of different second generation ethanol feedstocks from the tropics, and they are offering us a sneak preview of the preliminary results of the study they are writing.
'Second generation' biofuels are better known as 'lignocellulosic ethanol'. They differ from the first generation because they are not based on easily extractable sugars (as is the case with ethanol produced from sugar cane or corn). Instead, they are based on the cellulose and hemicellulose contained in biomass (a much broader category of feedstock - cellulose and hemicellulose are abundantly present in stalks, stover, fronds, wood, grass, crop residues,...almost in all forms of biomass).
To produce cellulosic ethanol, enzymes are used that break down the lignin that contains the (hemi)cellulose, after which the sugars (glucose in the case of cellulose, and pentose in the case of hemicellulose) are fermented and distilled to obtain ethanol. A good introduction can be found here.
In this context you may have heard about 'switchgrass' (Panicum virgatum) as being the potentially most productive feedstock for cellulosic ethanol. But when one looks at the energy balance of this crop (how much energy you put into producing the liquid fuel), then there are doubts about its usefulness.
Unexpected results
To our great surprise, the members found that the most productive ethanol crop is also the one that is best known as the most productive biodiesel crop: oil palm.
The African oil palm (Elaeis Guineensis) yields more vegetable oil than any other oleagenous plant. But what most people don't know is that the oil makes up only a mere 10% of the total amount of biomass that is harvested from a palm plantation each year. Such a plantation produces incredible amounts of biomass that are considered to be waste. It is these waste streams that contain vast amounts of cellulose and hemicellulose.
We are only teasing you and will ask you to be patient before we present the results of the study. But this much we can say: besides palm oil, the mere waste stream from Elaeis plantations yields more ethanol than switchgrass or sugarcane.
So not only is palm oil the most productive biodiesel crop, it is also the highest-yielding ethanol crop (provided cellulosic ethanol technologies are used). Moreover, one of the waste-streams can be used to produce vast amounts of biogas. This way, the oil palm is the energy crop that shows the highest energy balance of all energy crops ('Energy Returned on Energy Invested' is between 12 and 14), leaving all competitors far behind.
Cellulose-rich biomass
To conclude, we just give the reader a pointer about the total biomass that becomes available each year on one hectare of oil palm plantation, and the waste streams involved:
-25 tons of waste palm fronds, rich in hemicellulose, become available as the result of harvesting the palm fruits (this alone is more than switchgrass)
-3 to 4 tons of palm trunks become available (after a life-cycle of 25 years per tree, and at 150 trees per hectare), rich in hemicellulose and cellulose
-20 tons of fresh fruit bunches are harvested, containing the palm fruits
-of those 20 tons, 4 tons of crude palm oil and 1 ton of palm kernel oil is extracted
-of those 20 tons, 4.6 tons of empty fruit bunches, rich in cellulose and hemicellulose, become available
-of those 20 tons, 3 tons of press fibre become available (from the mesocarp of the fruit), also rich in cellulose
-of those 20 tons, 1.6 tons of palm kernel endocarp becomes available
-of those 20 tons, 1 ton of palm kernel press cake becomes available, rich in cellulose
-finally, the processing of the 20 tons of fresh fruit bunches, releases 100 tonnes of palm oil mill effluent, that yield 400 cubic metres of biogas
In the world of second generation biofuels, total biomass yield is the single most important factor determining the final energy balance of those green fuels. Palm oil already has a spectacular energy balance if used only for the production of biodiesel. But with the advent of cellulosic ethanol, this balance becomes out-of-this-world.
We can't wait to publish the results of our members' study, and we hope you'll be visiting our website when we do so.
Note: Obviously, we are well aware of the environmental problems associated with palm oil plantations, and we're the first to recognize this. But this doesn't do away the fact that in places where plantations already exist, it becomes important to exploit their full potential, which is not often the case. Especially in Africa, where old colonial-era plantations still exist, but have suffered under lack of investment and management, it is crucial to intensify and upgrade their production, instead of expanding the plantations and using new land. Second generation biofuels offer a tool to make this happen.
[Entry ends here.]
A group of BioPact members have been researching the potential of different second generation ethanol feedstocks from the tropics, and they are offering us a sneak preview of the preliminary results of the study they are writing.
'Second generation' biofuels are better known as 'lignocellulosic ethanol'. They differ from the first generation because they are not based on easily extractable sugars (as is the case with ethanol produced from sugar cane or corn). Instead, they are based on the cellulose and hemicellulose contained in biomass (a much broader category of feedstock - cellulose and hemicellulose are abundantly present in stalks, stover, fronds, wood, grass, crop residues,...almost in all forms of biomass).
To produce cellulosic ethanol, enzymes are used that break down the lignin that contains the (hemi)cellulose, after which the sugars (glucose in the case of cellulose, and pentose in the case of hemicellulose) are fermented and distilled to obtain ethanol. A good introduction can be found here.
In this context you may have heard about 'switchgrass' (Panicum virgatum) as being the potentially most productive feedstock for cellulosic ethanol. But when one looks at the energy balance of this crop (how much energy you put into producing the liquid fuel), then there are doubts about its usefulness.
Unexpected results
To our great surprise, the members found that the most productive ethanol crop is also the one that is best known as the most productive biodiesel crop: oil palm.
The African oil palm (Elaeis Guineensis) yields more vegetable oil than any other oleagenous plant. But what most people don't know is that the oil makes up only a mere 10% of the total amount of biomass that is harvested from a palm plantation each year. Such a plantation produces incredible amounts of biomass that are considered to be waste. It is these waste streams that contain vast amounts of cellulose and hemicellulose.
We are only teasing you and will ask you to be patient before we present the results of the study. But this much we can say: besides palm oil, the mere waste stream from Elaeis plantations yields more ethanol than switchgrass or sugarcane.
So not only is palm oil the most productive biodiesel crop, it is also the highest-yielding ethanol crop (provided cellulosic ethanol technologies are used). Moreover, one of the waste-streams can be used to produce vast amounts of biogas. This way, the oil palm is the energy crop that shows the highest energy balance of all energy crops ('Energy Returned on Energy Invested' is between 12 and 14), leaving all competitors far behind.
Cellulose-rich biomass
To conclude, we just give the reader a pointer about the total biomass that becomes available each year on one hectare of oil palm plantation, and the waste streams involved:
-25 tons of waste palm fronds, rich in hemicellulose, become available as the result of harvesting the palm fruits (this alone is more than switchgrass)
-3 to 4 tons of palm trunks become available (after a life-cycle of 25 years per tree, and at 150 trees per hectare), rich in hemicellulose and cellulose
-20 tons of fresh fruit bunches are harvested, containing the palm fruits
-of those 20 tons, 4 tons of crude palm oil and 1 ton of palm kernel oil is extracted
-of those 20 tons, 4.6 tons of empty fruit bunches, rich in cellulose and hemicellulose, become available
-of those 20 tons, 3 tons of press fibre become available (from the mesocarp of the fruit), also rich in cellulose
-of those 20 tons, 1.6 tons of palm kernel endocarp becomes available
-of those 20 tons, 1 ton of palm kernel press cake becomes available, rich in cellulose
-finally, the processing of the 20 tons of fresh fruit bunches, releases 100 tonnes of palm oil mill effluent, that yield 400 cubic metres of biogas
In the world of second generation biofuels, total biomass yield is the single most important factor determining the final energy balance of those green fuels. Palm oil already has a spectacular energy balance if used only for the production of biodiesel. But with the advent of cellulosic ethanol, this balance becomes out-of-this-world.
We can't wait to publish the results of our members' study, and we hope you'll be visiting our website when we do so.
Note: Obviously, we are well aware of the environmental problems associated with palm oil plantations, and we're the first to recognize this. But this doesn't do away the fact that in places where plantations already exist, it becomes important to exploit their full potential, which is not often the case. Especially in Africa, where old colonial-era plantations still exist, but have suffered under lack of investment and management, it is crucial to intensify and upgrade their production, instead of expanding the plantations and using new land. Second generation biofuels offer a tool to make this happen.
[Entry ends here.]
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