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AdeJones

Listed below are comments made by AdeJones between Wednesday, 3rd September 2008 and Sunday, 1st March 2009.

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Ethical Man's guide to making a fortune in a low-carbon world 5:17pm on 01 Mar 2009 This practice of composting manure?

It's not the best thing that you can do with it. The composting process produces a usable fertiliser, sure - but a better treatment is to anaerobically digest the sewage rather than compost it, and use the digestate as fertiliser instead. You can optimise the AD process to sterilise the digestate (thus achieving pathogen kill) and the carbon balance of the process is better than composting (because you are producing biogas in the process which you use to offset fossil fuel usage.)

Problems with contaminants are best dealt with at source by means of better regulation of the trade effluent discharges, and tighter control of domestic inputs (ie. toilet cleaners etc.)

The result of the AD process is biogas, a liquid digestate and a solid digestate. Ideal for agricultural landspreading - as indeed it is in the UK under the provisions of the Sewage Sludge To Land Regs.

None of this is new - the practice of using AD for treating sewage in the UK goes back to Victorian times, and there are tens of thousands of AD plants worldwide at all sorts of size ranges. We don't have that many AD plants in the UK, but the ones that we do have are mainly for the treatment of sewage sludge, so we're already doing this. Far better than retrofitting compost toilets across the UK for a population which largely isn't interested, and increasingly doesn't have the space for them anyway. Use the modern infrastructure that we've painstakingly developed over the last century and a half instead!
Two go mad in Silicon Valley... 11:16am on 31 Oct 2008 It's easy to cool a data centre. Build it next to a heat-only energy from waste plant, and use the spare heat to run absorption chillers. You win out several ways then, because you can :-

a.) Offset the impact of landfilling that residual (you should really recycle 70% plus of your waste - EfW is a residual treatment technology.)
b.) Offset the cost of generating electricity at 35% efficiency in fossil-fuel plants to inefficiently run refrigeration plant to cool these chillers (it works just as well on heat.)
c.) Ensures that the efficiency of the EfW plant is as high as possible (you can get over 70% efficiency on a 'heat-only' plant. Traditional EfW for electricity generation doesn't get to 20% net efficiencies. Waste isn't a terribly good fuel if you want to generate electricity due to its lowish calorific value.)
d.) Provide a year-round heat-sink for this EfW plant to use, without which you can't really run a 'heat-only' solution (even district heating tends to be very patchily used in the summer - conversely, this would be your highest demand for heat if you used absorption chillers.)

I've looked at the lifecycle assessment of this and the CO2 balances, and it's quite an elegant solution. The engineering is quite simple too.
All of a sudden... algae is everywhere 08:13am on 12 Oct 2008 #20 - you don't compost as part of anaerobic digestion. You can subject the solid digestate to further aerobic maturation if you wish (which is akin to composting), but it's not a given that you have to do this - it depends on the outcome you have in mind for this material (it can be landspread as it is). Maturation, as an aerobic process, does not produce methane. Indeed, composting, if you do it properly, does not produce methane either, other than in trace amounts.

The anaerobic digestion step does produce methane, but that's what you capture for energy recovery. As you are putting energy into an aerobic process to produce compost and CO2, and you are putting less energy into the anaerobic processing of this material to produce a biogas and digestates, and the biogas gets burned to produce energy and CO2, then it is easy to make a first principles calculation to demonstrate that AD has a better CO2 footprint than IVC.

Lots of work on this out there if you Google for it.
All of a sudden... algae is everywhere 09:19am on 11 Oct 2008 The real trick with algal biofuel production is to use it as an add-on to anaerobic digestion. AD is a means of processing segregated organic wastes, and the outputs are a modest amount of biogas, a solid and a liquid residue (known as digesates). The solid residue is a compost-like material, and can be used for the same applications as compost. The liquid residue is more problematic - it has reasonable levels of nutrients (N,P,K) but takes up a large volume in storage. It cannot be applied to land in wet weather, so your average AD plant needs a couple of months storage capacity (at least.)

When you burn the biogas in a gas engine to generate electricity, your outputs apart from electricity are hot water (from the cooling circuit of the engine) and CO2.

Oil-bearing algae need nutrient-rich water at a reasonable temperature plus elevated levels of CO2 for growth.

Now AD is already a carbon-negative technology, given that the energy produced outweighs the cost of collection of the organic wastes that feeds the plant. It is better than composting, and considerably more so than landfill. Harnessing oil-bearing algae to use the byproducts of AD offer the possibility of a strongly carbon-negative biofuel - and one which does not use crops, but instead uses wastes which would otherwise have a significant impact in landfill.

The downside lies with proving the technology - and the fact that two of the main rate controlling factors for algal growth in algae farms are surface area / volume ratio, and light intensity. Put bluntly, you need a big farm with a lot of tubes and good sunlight intensity to ensure that the efficiency of the process is maximised. If we crack this, we're onto a good thing. Were I an oil magnate, I would be putting money this way at this point in time. Whether or not this will work in the UK is a matter for discussion - I like to think it will, but I fear that we don't quite have enough sunlight to make this a viable year-round proposition.
Legalise Drugs! From maverick to mainstream 6:18pm on 04 Sep 2008 I'd comment on this article, but I have a serious attack of the munchies to attend to first ;-)
Beefed up 11:36am on 04 Sep 2008 #63 - you can, but...

In order to get the biogas into the supply, you have to clean it up first, and get it to the right calorific value. This means removing the CO2, any trace contaminants (ie. sulphur) and then possibly enriching it to get its CV up by a small amount. The gas grid regulators have exacting standards on the quality of gas.

The problem with this is that the CO2 removal equipment is not really commercially available at the scale of production from your average AD plant. So you either buy something oversized for the job, or look to build a very large AD plant to produce enough gas. Which then means sourcing a lot of material to feed it. Which might work in a very large urban area, but for a scalable dispersed technology like this isn't really viable elsewhere.

The other problem is that the Renewables Obligation Credits favour the use of electricity generation options, and the revenue from electricity generation (at c. £50/MW plus about £90/MW worth of ROC's - this equates to the theoretical return from about 3 tonnes of food waste) is much greater than the revenue from the biogas in the system (gas has about 1/3 the value of electricity.)

A promising third option is the use of biogas as a transport fuel. There is something known as the Road Transport Fuel Obligation here which will assist development of this area. Try http://www.cenex.co.uk/news-industryevents.asp for further info on this option (this company do a lot of work in this area - there are other companies out there doing likewise.)
The last post 6:13pm on 03 Sep 2008 #1 - if you'd followed the blog all the way through, you wouldn't have made such a silly post.

BTW - I've never met a chemist who can't spell 'substituted'. I think you're just a troll.
Top tips from plastic-free bloggers 4:40pm on 03 Sep 2008 #54 - but if you follow that chain of events, most things you could recycle could end up dumped like that. So why bother recycling?

A facile example, but you see where I'm coming from here? You have to divorce the material and the need to recycle it from the 'but x could happen' argument. The material and the need to recycle it aren't the problem here - it's ensuring that it is used appropriately.

As regards the impact of plastic thrown away as litter - again, it is not the material that is the issue, but the littering. Besides, packaging waste [including plastic bags] represents only 4% of litter.
Top tips from plastic-free bloggers 12:19pm on 03 Sep 2008 #52 - Do a google for 'The Garbage Project' or 'landfill archeology'. There are cases of people retrieving readable newspapers from American landfills that are over 50 years old.

If your landfill isn't that wet (and not all of them are), then you encapsulate a lot of this stuff for a long time. So the differential isn't as great as you'd believe.

Also, you need to factor in the impacts of discarding those bags, as a plastic bag in a landfill really doesn't do very much. A paper bag will rot in the anaerobic conditions and give you biogas. Which is 60% methane. You won't ever capture more than about 85-90% of it, and the rest will vent to atmosphere (the EU capture rate average is less than 50% according to recent research.)

That biogas has 23x the climate change potential of CO2. 1 tonne of organic waste will give you around 100m3 in landfill over time, subject to decay curves etc [in optimised AD, you'll get more - but landfill degradation isn't optimised.]

The other 40% of biogas is largely composed of CO2.

You have to factor in these impacts too.
One week in 08:22am on 03 Sep 2008 #86 - This isn't a criticism of the Comm/Industrial sector, btw - as this sector generally delivers greater recycling than the domestic waste sector. It's just that this is skewed by the larger companies.

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