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."

Comments

Higher usable energy

[moscow]

According to ABC Queensland , Macadamia shells are actually prime material for electricity generation - they burn more cleanly than coal, and produce more energy.

Of course, natural decay of the shells would release the CO2 in any case.

Re:Reduction in Co2?

[zmooc]

Wrong. The only thing that matters in this context, is the percentage of CO2 in the atmosphere. While in the long term, burning plants would indeed not introduce any new CO2 into the biosystem. The only problem is that it is generally assumed it takes about 100 years for nature to create a balance between CO2-production ans CO2-consumption by plants. Just compare it to a closed system in a box with a plant and a device burning it's seeds; the plant will consume the CO2 a lot slower than the device can produce it so the CO2-level in the box will definately go up just like a sink will fill when the tap runs faster than the drain can put up with.

But in the long term it's always better to burn plants instead of oil since burning oil introduces new C into our biosystem while burning plants only raises the C-level in the atmosphere but not in the biosystem.

By the way, this only works if you assume each burned plant will be replaced by a equivalent plant. Burning more plants means the average age and therefore size of plants will decrease and therefore the amount of C these plants can hold will also decrease. And then even the space that's available for plants is declining.

Re:The article doesn't say...

[madbastd]

But does anyone know why they chose macadamia nuts? Seems a very strange choice.

Macadamia trees are a native plant in that part of Australia, and grow very well. There's a large macadamia nut industry there, which was throwing out huge amounts of nutshell.

Re:Reduction in Co2?

[famebait]

Just compare it to a closed system in a box with a plant and a device burning it's seeds; the plant will consume the CO2 a lot slower than the device can produce it

What makes you believe that? Are you assuming that the plant produces seeds at a diminishing rate, or that burning a seed releases more carbon than was put into building it? Because something doesn't add up here.

You are describing a closed system with a net production of carbon. If you have one of those you could be very rich indeed.

Just like a sink will fill when the tap runs faster than the drain can put up with.

That's not a closed system.

The only problem is that it is generally assumed it takes about 100 years for nature to create a balance between CO2-production ans CO2-consumption by plants.

That's a little out of context. Yes, if you completely cut down a forest, it takes a long time until there is once again the same amount of biomass contained on that area. But we're not _removing_ the ecosystem and waiting for it to return here, we're burning a nutshell in stead of allowing it to rot. The tree is still there, and it doesn't take a 100 years to replace a nutshell. If you burn a billion shells a year and produce a billion too, you have a net emission of zero. You're basically just extracting solar energy, the shells and the carbon are just carriers in the process.

There would be an minor initial 'cost' in that you're shortening the cycle a little, releasing the carbon more shortly after it's trapped compared to natural decomposition. So you get an initial emission over the first year or two after start up, as the 'cache' of decomposing shells releases its carbon at the same time as new shells are burnt immediately. But after they're gone you'll be running in balance. Or you could avoid that too by imitating nature and storing the shells a couple of years before burning them.