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Power Plant Fueled By Nut Shells
sbszine writes "The Sydney Morning Herald is running an article about a green power plant that runs on the discarded shells of macadamia nuts. The power plant, located in Gympie, Queensland, is expected to reduce greenhouse gas emissions by around 9500 tonnes in its first year of operation."
How much energy goes into getting the nuts out of the shells in the first place? I remember going to a macadamia nut farm in Hawaii once. They had a prize of a lifetime supply of macadamias if you could get a nut out of a shell without using a saw. I tried smashing it with a rock with no luck. Apparently, no one had ever collected the prize.
Wrong wrong wrong. A nut grows in a single season. The carbon in the nut can only come from CO2 in the atmosphere. Therefore burning nuts is carbon neutral over a single nut-growing season.
Similarly, I fail to follow your example of a plant in a box. OK, while the seeds are actually aflame CO2 will be produced faster than it's being absorbed. But overall, the amount of carbon in the system is constant: anything which is not in the plant is in the atmosphere. Therefore so long as you burn the plant no more quickly than it grows, you'll never end up with a higher CO2 concentration than when you started.
Your argument only applies if you start burning something which has been growing for decades -- eg old-growth forest -- in which case you're releasing CO2 that took decades to remove from the atmosphere. But so long as you burn material grown only over, say, the last year -- eg fast-growing bamboo -- then the net amount of CO2 released into the atmosphere over that year must be zero.
The author of this post asserts his moral rights.
The main advantage in this case is that they were already growing the macadamia nuts in the area, and they were already shelling them. The shells were then, previously, just being discarded. Because the "fuel" for this power plant was previously considered "waste", the result is much more efficient economically then a lot of things.
Think of it like this:
macadamia = shell + nut
Old equasion:
profit = sale of nut - disposal of shell
New equasion:
profit = sale of nut + electricity generation from shell
This, of course, assumes that the electricity produced from the shells can be sold at a profit that is greater than the cost of disposing of the nuts. From everything I've heard here, the power plant is relatively inexpensive to construct ($3 million), as such, the cost of electricity generation probably won't be that great. However, we'd need more data to say that for sure.
As an added bonus, the CO2 output is neutral over a single year. Ie: shell takes 1 year's worth of CO2 in as it grows, we then burn it, and 1 years worth of CO2 is released. Comparatively, coal takes in X number of years (thousands of years ago), we burn it, and it releases it into the atmosphere now, resulting in a gain in CO2 in the atmosphere.
Keep in mind that this means we won't be powering the entire country with macadamia nut shells. This plant only powers 1200 homes. The brilliant aspect of this is that its powered off of waste that was already present in the region. This would be similar to a facility that produces corn creating a power plant next to it that is fueled by corn husks and the unedible parts of the corn. Its simply just a comparative advantage. Its fuel that you have here and now, so there are little to no transportation costs. Even if another biomass is more efficient, you'd have to transport it to the generation facility, decreasing its overall efficiency.
Ideally, for something like this, you'd build lots of smaller facilities, wherever burnable bio-waste is produced. 1200 homes here, 1200 homes there, mix it with some solar and wind generation, and other alternative energies, and eventually the fossil fuel habit might be kicked.