The box also produces carbon dioxide as a byproduct--a potential downside depending on how much it generates.
The amount it generates is of little concern - what matters is where the methane (or other fuel) comes from. If the methane is produced from fresh biomass then the box is carbon neutral. But if the fuel comes from oil then it won't be carbon neutral.
Which is a gross oversimplification since we know that biomass production is often anything but carbon neutral. Were petrochemical fetilizers involved? Did they clear land to produce it? How much oil was used to transport it? If it came from a landfill, was anything done to hasten decomposition, if so, it may be releasing CO2 that would otherwise have been locked up for much longer.
I appreciate the idea of getting maximum use from things that have already been produced, but I'm pretty down on scaling biofuels up. I think there are better uses of land and freshwater. In practice, photosynthesis just isn't that efficient, and then the plant takes a big cut for its own growth and maintainence. Finally, there generally multiple inneficient steps for transformation into useful work. It is dismal compared to solar + battery + electric motor.
Also, how much CO2 it generates depends only on the amount and type of fuel it consumes[1] - e.g. 1 CO2 molecule emitted per CH4 molecule consumed - so that statement is nonsensical to begin with.
[1] unless it also produces carbon monoxide, which is unlikely considering the efficiency claims. Other than H2O, I'm not aware of any other possible byproducts of methane oxidisation.
>> Other than H2O, I'm not aware of any other possible byproducts of methane oxidisation.
The same was said for the ICE, and now our cars emit all sorts of crud. Ideally, that's all you get: CH4 + O2 ---> 2H20 + CO2. Practically, you get sulfur and other impurities. Specifically sulfur scrubbers (http://www.duke-energy.com/environment/air-quality/sulfur-di...) are often used to reduce the amount of sulfur, but they raise the amount of CO2 byproduct. It's a no-win situation.
The sulfur is an impurity of the fuel, though, it's not produced out of thin air. How the engine deals with impurities will depend on the exact chemical reactions, but you're not going to get more CO2 molecules out than carbon atoms go in.
The amount of CO2 per unit of electricity produced is more the question. That would be a key element of its overall efficiency, although given its claimed efficiency, that number should be pretty good.
It looks like all the major Natural Gas exploration/development companies in the US are planning to drill like crazy in 2010/2011 which will likely drop the price of NG off a cliff.
So, fuel for this thing will be cheap in the near future (cheap for NG-fuel power plants too).
Not carbon-neutral though for those who are sensitive to environmental costs. For that, you'd have to set one up near a bio-methane plant or methane-capture facility. But really... there's no way a bunch of these things are going to pollute anything near what an equivalent coal-fired plant does. So adopting them would be a net win environmentalwise.
Where it gets interesting is in colder climates where the waste heat could be used for space heat and domestic hot water production, a.k.a. "combined heat and power".
Yeah I'm very interested in what the path to carbon neutrality is. I'm sure they've thought this through, obviously. Cow dung is probably not the end-game :)
The amount it generates is of little concern - what matters is where the methane (or other fuel) comes from. If the methane is produced from fresh biomass then the box is carbon neutral. But if the fuel comes from oil then it won't be carbon neutral.