gasification, biogas, mulching biochar
You touch on various topics that I have an interest in.
First: combustion of wood and other biomass for energy production.
The options break down as:
Co-Combustion of the biomass in coal power plants, displacing coal (no
Gasification (burning in limited oxygen supply, c.10% char)
Fast pyrolysis (no oxygen, a few minutes up to 650degC then rapid
quenching, c.30-40% char)
Slow pyrolysis (no oxygen, 350-600degC)
Charcoal-making (very slow pyrolysis at low end of temperature range,
gas product not used).
To see comparisons across the life cycle of different bio-energy,
bio-diesel and bio-electricity technologies, have a look at:
(Mortimer et al 2003, Elsayed et al 2003, Thornley et al 2009)
For a spreadsheet tool to compare biomass technologies including
electricity, heat and CHP generation, cofiring with fossil fuels,
anaerobic digestion, and liquid biofuels, see Biomass Environment
Assessment Tool 2 (Biomass Energy Centre 2008).
The challenge with pyrolysis/gasification and biochar is to be able to
predictably produce a standardised product, which can be tested for
composition and sold through agricultural outlets. Efforts in the UK
are being led by the UK Biochar Centre at Edinburgh University, and
you can get a sense of UK-wide activity by looking at the papers from
their last annual conference (available on the website). Biochar is
not available for sale in quantity in the UK at the moment. The
University of East Anglia will produce several hundred tons of
biochar/year when its new Biomass gasification CHP plant is in full
Regarding soil effects of biochar versus mulching, I am the chair of
the UK Permaculture Association’s Research Advisory Board so I have
been involved in setting up research systems to answer this sort of
question. Information is being made available through the Association
website (www.permaculture.org.uk), but the basic model is of a range
of experimental networks to which people and projects can subscribe
according to their capabilities. So we have a polyvegetable
experiment which you can carry out on 4m2 where we provide a
methodology and collect and analyse the results, a forest garden
programme, the LAND network for demonstration projects open to
visitors, and an embryonic farmer network.
The most easily demonstrable effects of biochar are its pH effect (it
is almost always alkaline, except when made from certain unusual
feedstocks like seaweed, so can be used in place of lime (about 30%
effectiveness by volume) on acid soils) and density effect affecting
drainage, improving it in clay soils and reducing it in sandy soils.
See the UKBRC conference papers for up-to-date trials and results.
The international Permaculture conference this year is in Jordan in
August, so the type of project that features in the video you
mentioned will be a prominent topic of attention there. What country
are you based in? – you mentioned rice husks.
On 8 April 2011 14:21, Nicholas Neal wrote:
> For me the other main advantage of CH4 is that we have years of experience
> working with it and an existing network to transport it.
> Under “gasification” (partial combustion) the principle products are CO and
> H2 with a bit of methane – reforming this to CH4 is difficult and expensive
> – there is an EU project which has looked at this but the costs were
> prohibitive – I’ll see if I can dig out the link to the project. Under
> “pyrolysis” (which is heating “without air” ) you generally get some solid
> (char) some liquid (tar) and some gas (methane, ethane).
> I’m not an expert on pyrolysis but I think with some effort you can tweek
> the process to change the proportions of gas, liquid and char. For woody
> biomass this might makes sense (because going the AD route means
> biochemically breaking up lignin and cellulose which can be tricky –
> although I’m about 15 years out of date on my knowledge in this area so
> maybe this is wrong – any comments from the group) but the trick is always
> to do something with the tars – either crack them to gases or condense them
> to char (otherwise you end up with a lot of black gloop which is difficult
> to handle). This ends up being something like a biomass distillation
> process. The biochar has potential use as a soil improver for acid soils, so
> could be a potential byproduct of value – infact there are quite a few
> organizations selling biochar it as we speak.
> I’m a little unsure about biochar, although I’m working on a project here
> where they use charred rice husk for in hydroponic systems for flower
> growing, and this works well. There are others that contend that its better
> to add biomass to soil as a mulch rather than char it, I’ve also heard that
> a mix of mulch and biochar is good – this is slightly tangential to the New
> gas discussion, but does anybody in the group have a view on biochar/mulch.
> Below is a video I came across on mulching (actually, more correctly
> permaculture) in the middle east – the results look impressive to me but
> would welcome an agronomists view.
> (sorry, this ended up being a bit random, but I hope interesting anyway)
> Nick N
> From: email@example.com
> [mailto:firstname.lastname@example.org] On Behalf Of Peter
> Sent: 08 April 2011 06:53
> To: email@example.com
> Subject: Re: The New Gas Age
> I too share the view that the future of low carbon transport is with gas,
> not electricity, although I contend that gas from renewable sources (those
> mentioned by Nick) will be a far better route than shale gas, with its huge
> environmental problems and climate change consequences.
> One issue I see is that we have potential surplus of off peak electricity
> from wind (and in the future tidal and hydrogen may be a better fuel than
> methane as it can be produced by electrolysis. I also understood that
> conventional forms of pyrolysis of waste produce carbon monoxide and
> hydrogen, not methane. I am not sure how easy it is to strip out the CO.
> Anaerobic digestion produces methane, not hydrogen. Of course, in purist
> terms, hydrogen is better than methane, as it does not produce CO2 on
> combustion, but is there a mixed economy here? I am also concerned that the
> article quoted talks about the “energy poverty” of sub-Saharan Africa, where
> solar resources are at their highest. Surely there is mileage in using these
> solar resources to produce gas, if they are too distant to make electricity
> for the high energy consuming countries effective?
> However, you will read in the UK government’s Energy National Policy
> Statement (E-NPS1), in spite of a series of representations on the issue,
> the use of gas as a low carbpon vehicle fuel is discounted in favour of
> electricity, thus justifying the need for more highly centralised generating
> capacity and hence new nuclear power. Shame that they do not seem to be
> taking into account all of the options when making decisions.