Skip links


Pub: Sydney Morning Herald

Pubdate: 14-Oct-1997

Edition: Late

Section: News And Features

Subsection: Arts

Page: 16

Wordcount: 1339

Diet of worms



IF (as has been said) the house is a symbol of self, what does it mean when a small inner-city terrace cuts itself off from all known services? Answer: not what you might think, in terms of social hermeticism. In fact, as gestures go this has to be one of the more heroically community-minded.

The good things in life never were free. We know that now. They were going up on the slate all along. Pretty soon the mere, cleanish presence of air/water/soil will set the meter ticking. It’s as outrageous as paying for school milk was a generation ago, but it’s coming.

Knowing this is one thing. But the combination of guilt and helplessness it generates still makes most of us look the other way. Too intractable, too depressing, too hard. Maybe the greenhouse thing is all furphy, anyway. Maybe the waste mountains will magically biodegrade and dolphins will develop some kind of tolerance to the nasties which gurgle down the daily plughole. Maybe they’ll come to like it.

Just as well there’s always someone eager to confront the beast in its lair. Michael Mobbs was an environmental solicitor-evangelist for years before he and partner Heather Armstrong decided to put money and mouth into closer proximity. Twelve months and $48,000 on, Mobbs is still sounding surprised by the way their brave experiment focuses the mind.

For the rest of us, the most upbeat possible response to a standard Sydney downpour is still to murmur piously about the agricultural benefits, then silently wish it to Spain. For the Mobbs-Armstrong household, any such soaking is cause for shameless glee. Mobbs chuckles like Scrooge McDuck (his own description) as raindrops roll like dollars into the tank.

The experiment had four goals: to become self-sufficient in water, to become a net exporter of clean energy and to allow no sewage or stormwater to leave the site. Sounds simple. But sustaining a four-person family on what you can harvest from the skies above a typical 5-metre wide Chippendale row-house, and what you can compost in its backyard, is no picnic.

So how does it work – and how well?

The systems themselves are frighteningly uncomplicated. Rain falls from God, is collected into closed, guano-free gutters and thence through a simple valve which allows the first, dusty rain to escape, funnelling the rest into an underground backyard tank. Initial thoughts had been to further filter the drinking water through carbon, but a monitoring program run by UTS’s Professor Geoffrey O’Loughlin has proved the water so pure that the filter was abandoned, even for the kids. STORMWATER collects in a mini wetland – all of four or five square metres worth, also in the backyard – where frogs, insects, native birds and various species of reed cohabit with every appearance of joie de vivre. Small as it is, the wetland can cope with several days of continuous Sydney deluge before sending any overflow onto the street.

The electricity system is based on the field of 18 solar panels covering the northern slopes of the terrace roof. A neat little device in the electrical box allows a two-way flow between the house and the national grid, so that every time the sun shines, the meter runs backwards.

But the truly staggering piece of household physiology is its digestion system. Sewage, grey-water (from sinks, dishwasher, showers) and kitchen compost all flush into a single tank, also submerged out back, where zillions of wrigglies and greeblies industriously reduce it all – doubt this at your peril – to nothing more than water and heat.

Worms poo, yes, but the castings help aerate the heap, and are themselves reduced by smaller and smaller microbes until only energy remains. The resultant water, after UV sterilisation, is faintly yellowish and reasonably high in nitrates and phosphates but contains zero faecal coliform. It can therefore be used to wash clothes, water the garden and service the perfectly middle-class Caroma dual-flush dunny. “It gives me hope,” says Mobbs, uncharacteristically wistful as he holds a glass of this home nectar to the light.

So, how does the house perform, on the ground? Not quite perfectly. The UTS monitoring team calculated the family would run out of water 20 per cent of the time. In fact, in the year so far, which included the driest April in 134 years of recorded data, there have been only three occasions on which the Mobbs-Armstrong fraternity have had to beg water from their neighbours. With a greater-than-80-square-metre roof, or abigger-than-38-square-metre garden (which limits the tank to 10,000-litres), even this contingency may have been avoidable.

The stormwater overflows very occasionally, and the net electricity flow is still, marginally, inward, although the household usage has dropped from 14kW a day to less than 4kW/day. Of this, more than 3kW/day (equivalent to three tonnes of coal a year) is sucked by the fridge alone. When finances allow the acquisition of a new, low-energy cooler, Mobbs expects the current $10-a-month electricity bill to fall to zero, or less. That would be something: what might a negative electricity bill look like? Banknotes?

The waste system is remarkably robust, coping happily with paper, cardboard, sanitary pads, condoms and anything else biodegradable. After nearly a year of operation, there is no visible increase in the heap of matter in the tank.

The worms and their colleagues, unlike so many pets, are also admirably tolerant of neglect. Go fishing for a month or six and the worms may get thinner, or fewer, but the heap won’t die, any more than your regular backyard compost dies. And, most jaw-dropping of all, there is no discernible aroma. Not even at the in-hole. ALL this enables the family to lead a normal, chaotic middle-class life of microwaves and music lessons, flushing, washing and using off-the-shelf shampoos and detergents just like anyone else. The house is unusual, but not so whacky as to affect its resale value.

What it doesn’t do is pay for itself. A cost-benefit analysis from the University NSW’s Professor Bob Walker shows that by the time the system costs are amortised by the savings they generate, it’ll be replacement time.

But on a bigger canvas the picture looks much more promising: to autonomise a single, small Chippendale terrace must be about as hard as it gets. Upscaled, especially to a green field site without existing services, the project’s net present value suddenly becomes positive – more than $18,000 per house, and more if you harness excess capacity.

Conventional services cost about $49,000 per house for water, sewerage and wiring. All the government/service providers need to do is stop subsidising conventional services or, in existing areas, offer an equal subsidy for conversion, and the future is immediately cleaner for all of us.

The next stage, now that we have the technology, as well as the incentive, is to address the poetics of sustainability. Just as Frank Lloyd Wright mastered the poetics of an earlier environmental technology, the way is now clear for a design sensibility which exploits the magic inherent in these new, eco-friendly dwelling systems. No longer need the sustainable house subsist on a style par with sensible shoes.

Not to cast any aspersions. The Mobbs-Armstrong house is admirable, comfortable and possessed of the most intensively high-minded backyard in the business. And you can shower when it’s cloudy.

Perfect or not, though, for each year of its existence this house saves 102,000 litres of clean Warragamba water and 4.3 tonnes of coal; keeps 80,000 litres of stormwater out of the harbour, 60,000 litres of sewage out of the ocean and 8.3 tonnes of carbon dioxide out of the air.

Imagine if we all did it.

The Mobbs-Armstrong house is open for weekly tours, phone 9310 2930.


Illus: Brave new world .



the environment-friendly Chippendale terrace house is almost self-sufficient in electricity and water.

Photograph by JAMES ALCOCK


Join the Discussion