Publications / Annual Report 2001
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There's more
to the muck than meets the eye It's an ugly sight that gives off an even uglier smell: a drainage ditch full of a foul blackish liquid with lumps of solid waste runs through the middle of the village. At intervals along its banks, households add their effluent to swell the flow. At the lower end of the village, the current slows as the ditch turns a corner and runs into a pond covered by an evil-looking brown crust. Here some of the contaminants in the water settle before the sluggish stream flows on, banked by fields, until it reaches the next village. The noxious cocktail carried by the ditch is a classic example of what economists call "negative externalities". Behind the euphemism lies a form of pollution that is a serious health hazard and a source of considerable resentment. "It's a running sore between communities and neighbors that can erupt at any time," says CIP anthropologist and SIUPA Coordinator Gordon Prain. What's in the cocktail? The wastewater is generated largely by an important source of employment and incomes in Greater Hanoi: processing of starch from cassava or canna. The starch is destined for a variety of products, including noodles, maltose and medicines. Starch processing is a complex multi-tiered industry through which thousands of poor peri-urban households supplement their meager farm earnings. They supply crude starch to wealthier enterprises that refine it or turn it into finished starch-based products. The industry has also spawned a multitude of support services, such as the manufacture of starch-making equipment, the supply of enzymes needed to break down starch into maltose, and transport and fuel supply. |
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Large amounts of water are used to process starch, producing a runoff that
carries a high proportion of suspended solids. CIP surveys in three
villages found that a single season's processing generated some 1.45
million cubic meters of wastewater containing physio-chemical and
microbiological contaminants in addition to nutrients such as nitrogen and
phosphorus. But these processing by-products are not the effluent's only
ingredients. Most of the households engaged in processing also raise pigs,
the source of a slurry that is rich in nitrogen but also contains the
bacterium Escherichia coli and a high count of worm eggs, both dangerous
to human health. Human excrement and household wastes make the mixture
even more potent. To make matters worse, most processing is carried out in
the dry season, so the effluent is little diluted with rainwater.
Starch making also produces solid wastes. Those from cassava - peel,
fibrous residue and low-quality "black" starch - are fed to
pigs, but canna residues, which do not have a high feed value, tend to be
unceremoniously dumped into streams or ponds where they add to the
pollution of wastewater, or, worse still, on roadsides outside people's
homes.
Working with Do Duc Ngai, of Vietnam's Institute of Ecology and Biological
Resources and CIP scientist Dai Peters, Prain began investigating the
effluent problem in 2000. Ngai and Peters selected four neighboring
villages in Greater Hanoi - Cat Que, Duong Lieu, Minh Khai and Son Duong -
three of which are centers for starch processing while the fourth, which
lies further downstream, was the main recipient of the industry's negative
externalities.
The project began by conducting a survey on attitudes to starch
processing. "Everyone, even in the processing villages, said that the
solid waste looked and smelled bad," says Peters. "Virtually all
the non-processors thought that it also harmed their health. And even 84
percent of the processors admitted as much." Most people in the
processing villages had had solid waste dumped outside their houses,
causing arguments with neighbors. As regards the liquid waste, residents
in the downstream, non-processing village frequently complained about the
pollution and nasty smells arriving via the drainage ditch, which
sometimes overflowed, flooding their homes. "They are clamoring for a
solution," says Peters.
"But whatever the problems created by starch processing, we must not
forget the importance of this activity to poor households," Peters
continues. "Processing more than doubles their incomes." The
extra cash earned directly from the starch, plus the value added to pig
production using the by-products as feed, more than offsets the reduction
in income caused by diverting labor away from crop production and other
activities. "Interventions aimed at cleaning up the environment for
the benefit of the public at large must do so without prejudicing the
economic interests of the individual processor," says Peters.
Turning a problem into an opportunity
The project's main activity has thus been to look for ways of cleaning the
wastewater and using it productively. The best potential use appeared to
be as nutrient-rich irrigation water for dry-season crops. If the nitrogen
and other nutrients in the water could replace some or all of the
purchased chemical fertilizers and manure that farmers apply to these
crops, the costs of production would fall, boosting profitability.
The challenge was to achieve this without increasing the risks to human
health. "This involves a subtle tradeoff," notes Prain.
"Processes that clean the water will also reduce its nutrient
content. The safer the water, the less it will raise crop yields."
To investigate the tradeoffs, Ngai and Peters conducted two sets of
experiments. The first was carried out using potted plants in the garden
of a village school. Concentrations form 0 to 100 percent of wastewater
were applied to the potted plants to determine how well the crops would
perform and what would happen to the soil. In the second experiment, the
researchers tested the effects of the timing and frequency of wastewater
applications in farmers' fields. They were interested in seeing whether it
was better to apply the wastewater to young plants during the first part
of the growing season or to more mature plants later in the season, and
whether weekly or fortnightly applications were better.
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Marketing canna roots and making starch and noodles are urban occupations |
A further important aim was to find out the effect of settling on the
quality and nutritive value of the water. To gauge this, the water was
passed from one field to another over successive weeks. In the pot trial,
the results were uniform across all the crops tested: the plants irrigated
with 80-100 percent wastewater had the highest yields. The soil's organic
matter content increased, suggesting that these yields could be sustained
or raised still further over time. Soil salinity also increased, but not
to a degree that would threaten crop productivity, at least in the short
term.
The results of the field trial showed that in terms of plant growth,
wastewater was most effective when it was applied once a week during the
early part of the growing season. This trial also shed light on best - and
safest - practices in use of wastewater for growing human food crops.
Researchers found that the window of opportunity comes after one week of
settling, when the amount of E. coli bacteria and worm eggs is greatly
reduced, but a sufficiently high nutrient content remains to make a
difference in yields. After two weeks of settling, the microbiological
contaminants have all but disappeared but the wastewater has also lost
much of its nutritive edge over ordinary irrigation water.
Two crops used
mainly to feed pigs, kangkung (Ipomea aquatica) and water taro (Colocasia
esculenta), responded particularly well to the trials. In the case of
kangkung, yields rose to an astounding 130 tons per hectare - more than
four times the yield achieved without wastewater. Water taro showed
similar, though less spectacular, gains. These yield increases could lower
the cost of feeding pigs, which seem to be immune to E. coli. But they
also suggest another promising way forward: the safest and most productive
use of wastewater could be achieved by passing it through a bed of
kangkung or water taro for a week, on its way to a rice plot. "This
way you clean the water in a way that adds no risk to human health, while
providing the rice with water that is still fairly rich in
nutrients," says Peters.
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Research on the best irrigation practices for different crops continues.
But whatever its outcome, only a certain proportion of village wastewater
can be recycled in this way. The rest still needs to be cleaned before it
passes on to other villages further downstream. The best opportunity for
doing this occurs at the downstream end of the processing villages, where
ponds or tanks slow the flow of the current. A "water
accounting" exercise conducted by the International Water Management
Institute, another partner in this project, found that some natural
cleaning takes place as the water moves through these areas. This process
could be improved by expanding the ponds or, more easily, by raising the
level of the outflow at the bottom end of the pond, thus slowing the rate
of flow still further. The next task will be to design and discuss
interventions of this kind with villagers, and then to introduce them for
testing.
Filling the gap
Problems of the kind researchers are investigating in Hanoi had received
only sporadic attention from the Future Harvest research centers until the
birth of the Systemwide Initiative on Urban and Peri-urban Agriculture in
1999.
"SIUPA is timely," says Prain, who coordinates the initiative.
"The past 30 years have seen an explosion in urban populations and
urban poverty. Peri-urban agriculture provides one of the few
opportunities open to new migrants to cities for earning cash
income," (see page 39). An estimated 800 million people already earn
their living in this way, a number that will continue to rise rapidly
through the first half of the twenty-first century.
SIUPA began its work by holding two stakeholder meetings, one in Asia and
the other in Sub-Saharan Africa. The Asian meeting selected Hanoi, where
CIP and other international research centers already had activities, as
the pilot city. In Africa, Yaounde, Kampala and Nairobi all emerged as
possible candidates, with Yaounde becoming the first to implement
activities, under the leadership of the International Institute of
Tropical Agriculture. In both regions, SIUPA conducts its work through
partnerships involving national and municipal research and development
groups, alongside international centers and organizations.
Peri-urban agriculture raises critical health and environmental issues
that must be tackled if we are to meet the challenges posed by the
broadening agenda of natural resources research. "It's a far cry from
yield trials on new potato varieties," says Prain. "But the
stronger partnerships made possible by SIUPA will enable us to make the
most of our resources to tackle these issues."
Migrant urban producers face conditions utterly different to those they may have known in the countryside from which they came. "Their overriding need is to make money fast," Prain notes. "In large part this reflects the struggle to get a foot on the ladder out of poverty in the new, highly competitive environment of the city, where nothing comes for free. But it also reflects the insecure land tenure and other risks they face." The land cultivated by peri-urban growers may be owned by speculators, who could drive them off it at any time; or it may be derelict land where soil and water resources have been poisoned by industry; or land left empty by other migrants because it is too close to a river and therefore subject to flash floods. Growers are often forced to cultivate roadsides, where passersby may steal the crop just as it reaches maturity. The commodities produced, and the management practices used, reflect these risks. The poorest, who face the most insecure conditions, choose crops that demand a low initial investment and that reach maturity quickly. One example is Chinese spinach, which can be harvested within 25 days of sowing. Because goats breed rapidly and can graze urban rubbish dumps and very poor pastures, they are the poorest's preferred livestock species. In contrast, more settled and secure households, where animals can be locked in at night, tend to graduate to sheep or crossbred cows. They may also invest a little in their enterprises, as the starch processors of Hanoi do. Management practices often show great ingenuity in adversity, while also incurring high risks. For instance, a frequent sight in some cities is the blocking or diversion of sewerage pipes or channels in order to irrigate vegetables - a practice that endangers the health of both producers and consumers. |
