The Good Oil: Coming soon to a household near you: waste digesters

Q:  Jack wants to know if it’s possible to get wastewater digesters which would deal with the sewage for an ordinary household.

These digesters, he writes, are not uncommon in China and India, but no one in New Zealand seems to know anything about them.

He says he’s been trying to find out something about them for a number of years, and says they are quite simple technology.  Basically they take organic matter and convert it into methane, which can be put to all sorts of uses.

A:  While at the moment the short answer is no, they’re not available here, that’s about to change.

The good news
 

Waikato engineer and practising environmental geological chemist Shane Carter is about to launch a household digester on to the New Zealand market.

He just has to write a thesis first.

Shane has about 25 years’ experience with methane production in various forms and has a great interest in sustainability.

The Morrinsville-based researcher says we have a bureaucratic mindset that is still in the 60s and 70s with regards to a lot of sustainable energy systems.

Methane digestion, he explains, is simple, but like everything else is complex to apply to our modern requirements.

“It’s easy to convert waste into methane, the object is to get the right temperature and mix of animal to vegetable waste.”

The difficult part is getting a continuous supply of gas that can be used in a modern household.

There are large commercial-sized digesters at work in New Zealand.  At the Horotiu landfill near Hamilton, gas fuels a gas engine that produces enough electricity to power the equivalent of 1000 homes.   And the city’s sewage treatment plant uses the biogas produced from treating sewage in a co-generation facility. 

Making the most of methane
 

A few years ago a journalist friend went to Chengdu, in Szechuan province, China.  While there she visited a prosperous farm (“He had several cows and several fields, but it was really peasant farming…”)

In the house, there was a room with a single wire wove bed, next to it one for cooking and other rooms held stock – chickens and pigs.

“I understand that the waste from the animals was put into a tank and the methane got piped into the cooking area, to run woks and the like.”

But here in New Zealand, there seem to be no digesters available for small households.

“The single family units used in India and China are batch systems and need a lot of human input to operate,” says Shane.  Avoiding too many technical details, he says a continuous digester is the best option.

Do it yourself
 

Ten years ago he built a stand alone unit for his house, which was designed to supply hot water to cowsheds or run a house.  It needs three cowpats a day, and now provides enough gas for hot water and a bench-top hob.

“You can feed human waste into the unit if plumbed correctly, the equivalent of four adults’ waste would produce about the same amount of gas.”

And there’s the bonus of the system producing good, sterile fertiliser. Trouble was, the cost was prohibitive – more than $7500. 

“To this end, I have designed a household model using different technology and new research results.  This should sell for about $1700 to $2000.”

He is about to strip down what he calls his prototype mule and make some modifications. “The new design has only one moving part.  I’m hoping the new unit will be popular as I’ve tried to make it simple, user-friendly and cheap.”

However, there’s a thesis on a novel way to remove colour from pulp and paper mill waste to complete at Waikato University, so he thinks it won’t be until after February before he finds time to work on a production model.

So – watch this space.  We will update developments as they happen.

… and now for something completely different

Jack also had a legal question.  He wanted to know about a Memorandum of Encumbrance, which an irrigation company has on the titles of farms that its water races go through.

What rights does the memorandum bestow?

Without hesitation, I got in touch with a hotshot international lawyer of my acquaintance.  The short answer Jack, is that a Memorandum of Encumbrance is just like any other legal document, it’s an agreement between two parties, and what it means depends on its precise wording.  

What the lawyer actually said

I am not making this up – this is word for word:

Dear Annette

The question is not what a memorandum of encumbrance is BUT what does the document say.

I can make up a number of names of things: a title of arrears, an arrears of title, a certificate of multiplicity, a bacchanalian redemptive mortgage, a synoptic preference executory schedule containing a preponderance of moronic legal draftsmen – etc.

BUT the simple key to any legal document is not found in what the preponderances call it but what is says.  You have to read it, or better still, I will read it for you.

That will be £750 please, no VAT because you are a resident outside the UK.  Thirty days otherwise we sue of course.

Lovely to hear from you

Best wishes
XXXX, BA LLB
Practicing Attorney and Lawyer in more places than you can shake a stick at

Lawyers.  Gotta love ’em.

© Annette Taylor

lifestyleblock.co.nz Investigative Free Range writer Annette Taylor will boldly search out answers to many of the perplexing questions that beset rural dwellers.
Unflinchingly she will seek out agricultural scientists, vets, lawyers, noise control officers and even politicians to answer those befuddling questions that you haven’t the time or inclination to chase.  No question too small, or too big.  Email Annette at This email address is being protected from spambots. You need JavaScript enabled to view it. and she will find the answers on your behalf.

 

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