If you believe too much CO2 is going to cause catastrophic climate change, then you’ll love this – we can use CO2 to increase the rate of plant growth; biofuel plants in particular.
How this will work in practice isn’t exactly clear. As we have noted, it will be a tragedy if we scrub CO2 out of our industrial emissions to stop possible global warming, while leaving unacceptable amounts of other airborne pollutants lower on the priority list. If you’re going to regulate CO2, while you’re at it, at least make sure you eliminate the carbon monoxide, lead, ozone, particulate matter, nitrogen dioxide, and sulpher dioxide, because we know they’re bad. Where I live in California, the summertime air is filthy, and it isn’t CO2.
In any case, one company that seems to have some good ideas as to how to use CO2 to grow biofuel is GS-CleanTech (the GS stands for “Green Shift”). On the page with their products and services overview, they make several interesting claims. Here’s one:
“GS CleanTech’s patented C02 Bioreactor reduces greenhouse gas emissions while creating an additional feedstock for renewable fuel production. If applied at ethanol facilities, it would boost fuel production by more than 15%, and if applied to coal fired power generation, it could produce more than 200 million gallons of renewable fuel annually for every 1,000 MW of electricity produced.”
The devil is always in the details. First of all, they probably mean “for every 1,000 megawatt-years of electricity produced.” So how much energy is in a megawatt-year, and how much energy is in 200 million gallons of renewable fuel?
Energy in 1,000 megawatt-years: Take 3,416 BTU’s (British Thermal Unit, our favorite way to do energy conversions) per kilowatt hour. Multiply by 24 hours per day, and 365 days per year. Now you have kilowatt-years. Multiply again to get megawatt-years, and then multiply again by 1,000 to get 1,000 megawatt years. Result: 29.9 billion.
Energy in 200 million gallons: A generous estimate of BTU’s per gallon of ethanol would be about 150,000. Multiply by 200 million. Result: 30 trillion.
This means GS-CleanTech is claiming they can get 1,000 times as much energy out of the CO2 produced by burning coal as they can get from the primary burning process – heat which drives a turbine which turns a generator and creates electricity. What CleanTech probably means is this quantity of CO2, as an appropriate portion of the many other inputs into a biofuel growing operation – solar energy, water, fertilizer – would be sufficient to produce 200 million gallons of energy. But that isn’t what they say. In any case, what about their growing operation? How much biofuel can they produce, and how?
GS-CleanTech’s product overview page goes on to say “CleanTech’s C02 Bioreactor can produce more than 200,000 gallons of fuel per acre (per year).” Right away they can’t possibly mean traditional farming – the best you can hope for from the best ethanol crops we’ve got on earth, sugar cane in Brazil, for example, is about 600 gallons per acre per year. So what are they thinking?
Check this out (paraphrasing): “C02 is piped to the bioreactor. Sunlight is collected with parabolic mirrors that transfer the light to light pipes which channel the light into the bioreactor structure where it is distributed and radiated using light panels. A growth media, such as polyester, is inserted between each lighting surface. Water, containing nutrients, continuously cascades down the growth media to facilitate the final required step for optimal growth.” You are encouraged to read their product overview page in its entirety.
Can such a “bioreactor structure,” using concentrated CO2, nutrient rich water, and distributed light, induce algae to grow at a rate literally 300 times greater than if the same area were only simple farmland? Maybe it can. We will see.
It’s interesting that in our earlier post “Biofuel vs. Photovoltaics” we reference claims of similar yields arising from researchers who intend to genetically engineer algae to produce extremely high yields of biofuel. GS-CleanTech is coming at this from a completely different direction. There is no way biofuel grown in traditional methods, jatropha in Africa, sugar cane in Brazil, etc., can replace crude oil (there isn’t enough land) even though in those places and elsewhere it can be produced cost competitively to crude oil. But if the productivity of algae to produce extremely high yields of biofuel is ever realized, it will be a game shifting development, kind of like cheap photovoltaics.