Bio: Mass, Gas, Diesel
And then there’s bio-mass, and the other bio-fuels. I wasn’t really convinced about bio-fuels: it seemed to me that if we burn anything in order to produce usable energy, then we will be generating atmospheric CO2, when we’re trying to reduce it, and if we grow anything, then it seems to me we’d be better off either eating it ourselves, letting our livestock eat it, letting wildlife eat it, or using it to feed the soil (by letting “mini beasts” eat it). I hadn’t done much in the way of research into bio-mass, but felt that if someone did persuade me, then we could probably hook our bio-fuel generation facility into our micro-grid.
And then I was persuaded!
First, let’s deal with the issue of generating CO2 when we burn biological material. It’s true; we do. However, when we burn coal or oil we are releasing CO2 into the atmosphere that was bound up millions of years ago, so as far as we are concerned right now, this is a net increase in CO2. However, if we (say) burn straw, then the CO2 we’re releasing was only taken out of the atmosphere a few months ago. And if we plant something else that’s growing as we harvest that straw, then the process is net carbon neutral. This is very nicely explained in this little video from YouGen (but bear in mind that the video was made in 2012: economics will have changed).
(FairEnergy.org.uk appear to have vanished)
It does leave the question of “wouldn’t there be something else we could do with that biomass material?”, but if we use wood pellets made from the waste of sawmills which are processing the output of sustainably-managed woodland (and wood pellets seem to be the easiest and most energy efficient material to use), then a biomass source of energy would seem like a reasonable use for that material.
Given that we probably need little or no heating for the Foldehampton domestic homes, because they are built to PassivHaus standards, we would probably use BioMass mainly in the colder part of the year for improving the background temperature in the larger buildings on site: the community buildings, the garden centre, restaurant, hotel, keep fit and health centre and so on, although they will also be built with high levels of insulation, heat recovery and with solar panels. Heating a swimming pool and whirl-pool bath could be a good use, too!
Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste and/or to produce fuels. Wikipedia.
There seem to be three distinct areas of AD:
- AD from Food Waste (mostly local councils, dealing with the contents of green wheelie bins, plus supermarket food waste)
- AD from Farm Waste (farms dealing with animal slurry and crop waste)
- AD from Human Waste (sewerage).
As far as I can see, the processes are very similar, here are links talking about food waste and farm waste. Nearly all the references that I can find for human waste are light-hearted newspaper articles about how a local bus is being run on “pooh power”.
In order to use bio-gas to run vehicles, the gas has to be cleaned and compressed to quite a high level, which in itself takes energy.
The gas could be used more directly for heat (a frequent suggestion is to use it for cooking, but that would involve a much higher level of on-site infrastructure, as we would have to run pipes to every house.).
It could also be used to power a Combined Heat and Power (CHP) plant to provide electricity and heat to some of the commercial buildings on site (community building, retail barn, hotel, restaurant, health centre, etc).
I’m not sure that there’s much use for bio-diesel at Foldehampton, unless someone wants to persuade me otherwise, but here’s an interesting news article from the BBC on the subject: ”Waste products, not crops, key to boosting UK biofuels”.