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."

Re:The article doesn't say...

[bhima]

Because they are processing the nuts there and the shells are a waste product.

Also they are very tasty!

Higher usable energy

[moscow]

According to ABC Queensland [abc.net.au], 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...

[Anonymous Coward]

Macadamia nuts are produced in great quantities in Queensland...

Re:The article doesn't say...

[Thomas M Hughes]

My understanding is they had an existing facility that shells and cans macadamia nuts, and previously the shells were just being discarded as waste product. Someone had the bright idea to use the waste shells as fuel for a power plant. Basically, they just turned an expense (waste disposal) into a profit (electricity generation). And the facility only cost $3 million to create. All in all, I think this was an absolutely brilliant move.

Re:The article doesn't say...

[madbastd]

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

Macadamia trees [crfg.org] 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?

[Anonymous Coward]

how would you transmit the power back to earth? Pay to have batteries shipped over? Or maybe invent that wireless power supply that i've been hankering for all these years?

Microwaves..... and im not talking about ovens.

Re:Reduction in Co2?

[bernywork]

It also reduces the requirement on burning coal something we do WAY to much of here in Aus.

Basically it would also be a comparison in producing the same amount of energy from burning coal vs. macadamia shells.

Re:nice prediction

[The Famous Druid]

Well, a few months ago, I was working in the electricity biz in QLD, and I can assure you that they are not nearing their generation limits at the moment.

However, the power grid is very long and thin (just about everyone lives on or near the coast) and most of the existing generators are not all that conveniently close to the main demand centres, so they sometimes have problems shuffling the power about to get to where it's needed.

My guess is that this new station will help aleviate that problem.

Re:Is the concept really that unclear?

[Disevidence]

Correct. QLD has a very large macadamia nut industry, as the plant is native and our climate well-suited to it.

Re:Reduction in Co2?

[Disevidence]

I hate to tell you this, but the shells of the nuts are going to decay anyway, releasing the carbon into the biosphere. So why not speed the process up, and generate some cheap electricity.

Re:Reduction in Co2?

[zmooc]

Because, like I said, it's about the % of CO2 in the biosystem which will stay lower if the C is kept in the biomass longer. You're not looking at it as if it's a closed system, while it is (with regard to C, at least).

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.

Re:Reduction in Co2?

[DrXym]

Potentially it is carbon neutral, but presumably the nuts need transporting, processing etc. so it isn't really. Still, it is miles better than burning fossil fuels.

Wow 1.5MW

[edison490]

Holy cow! A whole 1.5MW. Lets see, thats about enough to power 100 homes!

Re:Are you suggesting burning rubbish?

[ajs318]

Not true. Extreme heat destroys dioxins. They are often created by partial combustion {think bonfire}. What is basically going on in a fire is two processes. Pyrolysis is the fuel being decomposed into simpler chemicals, almost always incomplete fragments {sometimes even individual atoms} which will bond with whatever is nearest to hand {strictly speaking, nearest to valence electron?} as soon as they cool down enough. Pyrolysis consumes energy in breaking chemical bonds. Oxidation is the simpler chemicals reacting with oxygen. This gives out energy. Oxygen is chemically very horny and also will try very hard to avoid having to share with anything else. The pyrolysis products undergo some further decomposition as the oxygen atoms each try to grab something for themselves. Since the oxidation puts out more energy than the pyrolysis required, the fire stays alight. But you have to put some energy in {typically from a match} to start the pyrolysis, otherwise you would get spontaneous combustion.

Now, in a bonfire or badly-designed furnace, the pyrolysis products cool and recombine into literally goodness-knows-what and escape before they get a chance to combine with oxygen. This is where incineration can fail. Large lumps of fuel, and mixed fuels, all exacerbate the problems.

In a well-designed furnace, the fuel is finely-divided and the air supply forced {an unattended fire will tend to produce only as much energy as it needs to stay alight; this may mean partial combustion with great quantities of chemicals being released. A fan requires energy, but MOTN the energy gain from fetter combustion is greater than the consumption of the motor}. If the fuel is very heterogeneous, the pyrolysis phase of the reaction can be completed separately in by heating the fuel in an airless chamber {consuming energy} and the pyrolysis products burned later {releasing more energy than it took to do the pyrolysis}. By adjusting the temperature and pressure you can select whether the intermediate product is a gas, a light liquid like petrol or a heavy liquid like diesel fuel. This has the advantage that you know how long is the longest carbon chain in the fuel for the next stage, and there is no way that the products can contain sny longer carbon chains. The disadvantage is that it distributes the high-temperature processes, thereby creating more opportunities for heat leakage.

As for the "plastics" argument, it's a red herring. Upstream segregation could be used to separate plastic from the waste being used for energy recovery, if you were really concerned. But I can't see how it would not be better to extract energy from plastic that has already been used for something, than to use up energy burying that plastic in landfill and digging up more fossil fuel just to burn for energy. Over time, as fossil fuels became more expensive, plastics would begin to be made from plants anyway. Not to mention that lanfills also produce dioxins, albeit more slowly, and organic matter in landfill decays to CH4, which, molecule-for-molecule, is a better heat trap than CO2. The real problem is ignorance of the First Law of Thermodynamics. We've already had people bitching about CO2 emissions like they don't know where the carbon in a plant comes from, and if people can't appreciate the First Law as it applies to the tangible form of matter, how can we suppose they can appreciate it as applied to energy?

Of course, I'm with you about reduction. My ex's daughter was raised in reusable cotton nappies, so will be my niece at least while she is stopping with me. I avoid single-serving packs whenever possible. I wipe my nose on yesterday's T-shirt, and I put my sandwiches straight in my lunchbox without using a polybag {in the absence of a satisfactory explanation as to how wrapping food in plastic saves me from risking cancer by letting it touch plastic}. I don't use sanitary towels either, but only for The Reason That Does Not Count.

Re:Energy in/Energy out.

[N Monkey]

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.

My primary school (in Brisbane, QLD) had Macadamia tree in the grounds so I got a lot of practice...

The shells are damned tough. You DON'T want to use a saw (too much work!). It's difficult to use a (lump/sledge) hammer because you can't hit it hard enough to break the shell and NOT pulverise the kernel. For a while I used a really big vice on my Dad's work bench. That way you could apply a huge force that would only operate over a very short distance.

Many of the commercial home nut crackers use a hammer and an anvil with a hole that the nut sits inside with only a small part protruding. That way the hammer cracks the shell and then is decelerated before destroying the kernel.

Simon

Re:Reduction in Co2?

[shokk]

Bullshit. Plants absorb quite a bit of carbon from the ground. That's a lot of old carbon that's released there. They estimate about 30% of the plant is old carbon.

http://www.sciencenet.org.uk/database/earth/natura lenvironment/e00077d.html [sciencenet.org.uk]

More nuts per square kilometre...

[Anonymous Coward]

This power plant is perfectly situated. As all Queenslanders know, there are more nuts per square kilometre in Gympie than anywhere else in the state. In fact, Gympie is runner up to Canberra which has the highest population of nuts in Australia.

Seriously, as SE Queensland / NE New South Wales is the original home of the macadamia there are huge plantations in the region. Sourcing enough waste shells to run this plant will NOT be a problem.

The local TV reports about this power plant stated that the energy output from macadamia shells was roughly equivalent to coal, weight for weight.

Finally, responding to the posts about just how to open these nuts. A vice is the best. Apply a large amount of pressure, slowly, and the shell cracks neatly in half. Here in Oz we have hand held devices that allow us to open these beauties in the lounge chair, watching football, without disturbing the beer on the coffee table.

It's been done before

[Teknikill]

I worked for Cratech, they built the 'Green Machine', it takes (cotton) gin trash and converts into gases and activated carbon (for water filters) and the gases are burned in a generator to produce electricity. Here's a link [westbioenergy.org] to that very process and pictures of the machine I helped build. This process could be used to convert almost any biomass fuel into electricity.

Re:Higher usable energy

[mpe]

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

The decay process can also produce methane. Which is worst "greenhouse gas" than carbon dioxide.

Wood Burning Power Plant in West Aust

[Anonymous Coward]

See this link

http://www.westernpower.com.au/html/home/environ me nt/renewable_energy/renewable_bioenergy.html

for a wood burning power station with by products and synergies. This is in Western Australia and is small at 1 MW export, but a 10 MW is planned next. I worked there for a while on construction and have seen the whole setup.

Sociological

[sasah]

It is likely that most large-scale monocultural industires can (economically) convert their waste products into something useful. Such innovation is occuring in the poultry industry now [see citations below]. However, I have deep seated doubt that any of these technologies will be implemented on a national scale until the majority of the populace reckognizes the need to use available resources more efficently.

Jouney to Fuel [journeytoforever.org] | Chicken Manure Fuel

Anything into Oil [discover.com] | Discover

Been there, done that...

[allanj]

I've had a stoker furnace in my home for 5 years now, and it has burned a variety of waste products with great success:

• Hazelnut shells
• Compressed sawdust
• Cherry nucleus shells
• Olive oil nucleus shells
• Wheat - unfit for consumption for various reasons
• "Oilcakes" - byproducts from animal protein feed production
• Pea byproducts

So in short, YOU can do this too - but probably not in metro areas. Get a stoker furnace, a form of storage, contact some of the local farming industries around and start heating your home with other people's waste products - safely and very economically.

Lots of farming industries produce big amounts of waste, and most of that can be converted into biofuel simply by drying and sometimes crushing/shredding.

Or get a wood shredder and go shred the wood from trees that have fallen down in storms/hurricanes/whatever hits your region the most - many people will gladly let you remove their fallen trees, and you can heat your house very economically in this way.