Turning sewage into soil

By JAN CORBETT and JAMES GARDINER

The announcement curdled in the veins of local environmental lobbyists and had at least two government ministries vowing to fight.

Last month the Living Earth company, sponsor of television's Maggie's Garden Show, announced its desire to turn Aucklanders' sewage into garden compost.

With its larger rubbish-disposing partner, Waste Management Ltd, it has formed the Living Earth Joint Venture, a company which already sells compost made from human excrement in Wellington, and has its sights on Christchurch's sewage-treatment byproducts.

As international demands grow for cleaner waterways, the mountains of sludge being extracted from sewage are growing rapidly. But that coincides with vociferous calls for reduced waste volumes through better management and recycling.

Policy advisers in the Environment Ministry and the Agriculture and Forestry Ministry are nervous about sludge being returned to the soil when it
harbours contaminants such as heavy metals and dioxins which could enter the food chain if the land is later used for grazing.

They are particularly concerned that the Wellington Regional Council has raised the allowable contaminant levels for this compost, against the advice of its officials.

Groups as diverse as Federated Farmers and environmentalists Friends of the Earth fear the precedent set in Wellington will be replicated nationwide, threatening our meat and dairy trade to countries with stringent contaminant levels on their imports, and possibly leaving contaminated sites for future generations.

The Agriculture and Fisheries Ministry's biggest worry is the effect raising contaminant levels in soil will have on trade. Decades of reliance on superphosphate have built up cadmium in sheep livers to the degree that those from animals older than two and a half years cannot be exported.

Considerable effort has gone into reducing cadmium in superphosphate and the ministry does not want to see that work undermined. It wants farmers using biosolid compost to be required to lodge management plans.

The Environment Ministry's main concern is lethal dioxins entering the food chain. Senior policy analyst Dr Simon Buckland says the risk is not from growing food on the compost, but if the same land is later used for grazing. Dioxins are swallowed by sheep and
cattle and become concentrated in their fat, exposing humans when they consume the meat.

Which is why Federated Farmers and the Dairy Research Institute also have concerns.

The federation's executive director of policy, Catherine Petrey, says animals ingest a surprising amount of soil when they graze. The federation would like a warning that any compost containing sewage sludge should not be used on pastures. In the absence of such warnings, Petrey says the dairy industry is telling farmers not to use it.

"The question is whether we have adequate controls and information so that we're not creating a problem for tomorrow."

She says the federation has not been involved in the Wellington consents but will be watching for applications lodged elsewhere.

Meriel Watts, of organic gardening and farming proponents the Soil and Health Association, says her organisation will fight on the Auckland front also, particularly because of the dieldrin, DDT and DDE levels in the sludge (DDE is what DDT becomes as it breaks down). They accumulate in the soil.

Watts has concerns about people using the sewage sludge on home gardens because these contaminants can be taken up by fruits and vegetables "or they can simply be eaten by small children who often eat dirt."

She says New Zealand already has a problem with international markets because of relatively high levels of DDT in our soils. Putting sewage sludge on agricultural land ruins our ability to become an internationally recognised fully organic food producer — the association's 25-year goal.

But who says the levels are dangerous?

One of the problems with soil contaminants is a lack of accepted standards. A review of the 1992 guidelines by the industry body, the Water and Waste Association, with taxpayer funding from the Environment Ministry, drew up new, stricter proposals.

Some argue that those guidelines, if adopted, would prevent any sewage sludge being applied to land. There was also industry opposition and the ministry, citing a failure to consult sufficiently widely, effectively told the association to try again.

Set against those concerns are the opinions of two heavy-metal experts, Professor Ron McLaren of Lincoln University and Dr Tom Speir of the Environmental Science and Research Institute, who gave evidence for Living Earth when it applied for resource consent for the higher contaminant levels.

They insist that if the correct amount of compost is applied to the soil, it will take longer than 25 years — the duration of the resource consent — before the contaminants exceed the 1992 guidelines. In that time, says McLaren, more research should have been done and the heavy metal content in sewage should have been reduced sufficiently by environmentally conscious local bodies to eradicate any long-term problems.

Where McLaren and Speir foresee a problem is if gardeners use the compost as a soil substitute. That would give them soil with contaminant levels higher than the Health Ministry's 1992 guidelines recommend.

At present, there is nothing on the labelling warning gardeners not to use the compost as soil. Nor did the regional council make regular soil monitoring a requirement of the consent, as McLaren suggested. But it did agree to the Environment Ministry's request that a register be kept of bulk users.

Bob Tait, of Friends of the Earth, says its main objection is to the contaminants. He thinks Living Earth should specify the exact contents and how to safely use the product.

He adds that under certain conditions the pathogens — bacteria and viruses — in human waste could re-establish themselves, even though most are killed off during the composting process.

However, that view is not accepted by the Wellington Medical Officer of Health, Dr Stephen Palmer, who pronounces himself satisfied that pathogens are not an issue.

For scientists like Speir and McLaren, it is a question of balancing the risk of contaminants against the benefits of recycling the rich nutrients in the sewage sludge. It also solves the problem of what to do with the ever-increasing mountains of sludge.

As sewage treatment became more common and more efficient, mountains of biosolids piled up across developed countries. The solution to one environmental problem created another. Pumping it out to sea, bulldozing it into landfill or burning it all damage the environment.

Plough it back into the garden? Now that was a possibility. Surely that is what nature intended. Dung from humans and animals has been recognised as valuable fertiliser for thousands of years. The problem is that human waste, which can be rendered hygienic within about 30 days, gets mixed in the same sewerage system as the chemicals and heavy metals from industry, household detergents, cleaning products and even the dyes from cheap, imported T-shirts.

But before marketers had any chance of convincing the average home gardener to take a bag of it home for the tomatoes or the petunia patch, they had to come up with a more palatable name. After the American spin-doctors got elbow-deep in it, the fetid, slimy leftovers from treating raw sewage became known by the more palatable term, biosolids.

What it is, of course, is excrement, mixed with the heavy metals from stormwater runoff.

Auckland's Mangere sewage treatment plant produces around 100 tonnes of biosolids daily. The new, more efficient plant will extract three times as much.

Right now the sludge, which is treated and has lime added, is mostly being used to restore the coastal areas around the old plant. But Watercare Services, the company owned by the six greater Auckland councils, knows that before long it will have to find some other way of disposing of the biosolids.

Already the joint venture is lobbying the councils and Watercare acknowledges its waste-into-compost proposal is one it will consider, although the options will not be narrowed down for another year.

North Shore City, producing 20 tonnes of sludge daily, is facing the same question, as is Rodney District (eight tonnes). Both dump it in landfills.

North Shore councillor Dr Joel Cayford, deputy chairman of the works and environment committee, says the council has been looking at the Living Earth composting option.

After reading a report the committee commissioned on the proposal, he is less enamoured of the idea. "We've been advised there are problems with this approach because of the contaminants."

The council cannot control how people use the compost. "The advice I'm seeing is that it would be irresponsible to let it out of our control."

An alternative is to spread the sludge across forest land, away from public areas, and monitor whether it leaches into groundwater.

Rob Fenwick, director and spokesman for Living Earth, used to work in public relations, so if anyone knows how to accentuate the positive, it is he.

Sitting in the boardroom of Living Earth's head office in the industrial area of Lunn Ave, Mt Wellington, he scoops up a handful of the Wellington-made compost and offers to eat it.

He acknowledges the uncertainties but says he is convinced that recycling biosolids is the right thing to do — certainly a far preferable option to dumping or burning it.

He points to outside agencies such as the World Wildlife Fund, Forest and Bird Protection Society and the Maruia Society which supported the original application to the Wellington Regional Council, but then concedes he is a trustee of WWF, a member of Forest and Bird and closely aligned with the Maruia Society kingpin Guy Salmon, with whom he founded the now-defunct Progressive Greens political party in 1996.

Fenwick is also a director of Landcare Research, which is working with the ESR on research into use of sewage sludge, and the Water and Waste Association, which drafted the rejected guidelines.

"The one thing we recognised from the outset was we would have to be market-led rather than waste-driven," Fenwick says.

"The commercial graveyard is littered with people who went into the recycling business without being sure that they could have a sustainable commercial market for the finished product. That's why we've been so focused on branding and quality and selling beautiful gardens."

But although they "don't hide" the fact the Wellington-made compost contains human waste, "we don't think it's one of the main, competitive market advantages."

Fenwick points out that levels set for heavy metals in compost are actually lower than the levels allowed for some foods.

"From where I sit, at least the product has a quality standard. I don't want any bloody heavy metals in my compost; I want the best stuff I can, so I'm religiously watching the quality of the effluent. In the past, when it was being pumped into the ocean and out of sight out of mind, nobody gave a stuff."

The opportunity to expand in Auckland arises from the city councils' waste-reduction policies. Like all world cities, they have a goal of reducing waste by cutting the amount of organic waste that goes into landfills, and finding ways of safely disposing of dangerous toxins.

Clearly, Fenwick will need all his powers of persuasion to convince the rest of New Zealand to follow Welling-ton. He says the decision in Auckland is for Watercare, but of course regional councillors will ultimately decide what can be done and under what conditions.

The thrust of Fenwick's message to them is:

"Each year New Zealand loses 400 million tonnes of topsoil into the ocean and topsoil takes about 1000 years a centimetre to create, and that is really the lifeblood of our economy. That's why I feel very comfortable that what we are doing is producing a net environmental and economic benefit to the land. It's what nature intended us to do."