New Engineer: Toxic Waste in Fertiliser

Citation: Sharon Beder, Recycling can be a dirty business, Engineers Australia, October 2001, p. 42.

This is a final version submitted for publication. Minor editorial changes may have subsequently been made.

There is a long history, dating back at least to the 19th Century, of companies using innovative and not altogether responsible methods to get rid of their waste products.

Between 1856 and 1876 it is estimated that over 400 patents were granted for chemical precipitants for sewage treatment. Often the precipitants were unwanted by-products of industrial processes used with some other material. A writer at the time observed: "Inventors seem mainly to have looked out for articles which were cheap, or entirely worthless, and heaped them together without any definite notion of the part which they were separately and collectively to play. This alone can count for the recommendation of such bodies as coal-ashes, soot, salt, gypsum, etc., which in almost every case would do more harm than good."

A book published last month entitled "Fateful Harvest" describes how industrial waste in the US has been routinely recycled as fertiliser to be spread over the farms of America. Based on a 1997 series of articles in the Seattle Times by Duff Wilson, the book describes how, in the many states of the US, any material that has fertilising properties can be labelled a fertilizer, even if it contains heavy metals and other dangerous chemicals.

As landfill space became scarce in the US, companies saw the benefits of relabelling their hazardous wastes as fertiliser ingredients. Wastes from smelters, mining, cement kilns, wood-product slurries, incinerator wastes and other industrial wastes could be legally added to fertilisers in many states.

Duff gave various examples, including the way "a dark powder from two Oregon steel mills is poured from rail cars into the top of silos" and stored as hazardous waste. It is then "taken out of the bottom of the silos as a raw material for fertilizer". He described how low-level radioactive waste was disposed of in Oklahoma by "licensing it as a liquid fertilizer and spraying it over 9,000 acres of grazing land".

"Among the substances found in some recycled fertilizers are cadmium, lead, arsenic, radionuclides and dioxins, at levels some scientists say may pose a threat to human health." These substances could pose a danger to farm workers as well as consumers who eat the crops grown on farms fertilised in this way. They can also damage the crops themselves and contaminate ground water.

According to the Environmental Working Group, a non-profit enviornmental research organisation in Washington DC, 600 companies from 44 states were involved in this practice between 1990 and 1995. Of the 270 million pounds of toxic waste they sent to farms and fertiliser companies, 30% came from the steel industry.

Fertilisers in the US are not required to be labelled with their source nor with all their ingredients, not even toxic ingredients. So farmers were completely unaware of the practice until some farmers whose crop yields were significantly down and whose cattle were dying of cancer started making enquiries. The practice still continues and last month the US EPA held a national public hearing in Seattle into the issue of toxic waste in fertilizers.

Whilst Australian fertilisers have traditionally been derived from oceanic island deposits, they are increasingly being imported from overseas, including from the USA. Regulation of heavy metals in fertilisers is done at the state level and varies significantly, the most common limits are on Cadmium. Most states also have guidelines for the use of biosolids (sewage sludges) as fertilisers to prevent metal accumulation in the food chain and adverse consequences for crops.

CSIRO researchers recently pointed out that there is increasing pressure in Australia to divert urban wastes from landfill for application to agricultural soils. "Land disposal of biosolids has the potential to contaminate large areas of land... In Australia, we estimate that in excess of 175 000 t [tonnes] dry biosolids are produced each year by the major metropolitan water authorities, and É agricultural reuse is likely to increase in the future."

References:

Duff Wilson, "Fateful Harvest: the True Story of a Small Town, a Global Industry, and a Toxic Secret", Harper Collins, 2001.

M. J. McLaughlin et al, ‘Review: A bioavailability-based rationale for controlling metal and metalloid contamination of agricultural land in Australia and New Zealand’, Aust. J. of Soil Res., 38, 2000, pp. 1037-86.