Turning industrial waste into compost
A successful environmental-protection and resource-conservation
project in Brazil
by Winfried Schmidt
Citrus farmers in the Vale do Cai region of Porto Alegre's
hinterland who switched to ecofarming have set up their own company that is
developing a method of turning organic waste from the region into compost by
aerobic fermentation. The compost is to be distributed among the shareholders.
Consultancy is being provided to the farmers via a GTZ-supported scheme.
Composting residues from the food industry is an economically
viable approach to disposal and supplies ecofarmers with low-cost fertiliser for
their citrus crops. The GTZ-assisted project in Brazil has succeeded in
combining environmental protection with economic interests. The author describes
how these successful measures took root.
Most foods consumed and exported by Brazil are produced and
processed by the agro-industries in the Federal State of Rio Grande do Sul.
Enormous dumps of organic waste are scattered over the State.
Enforcing stricter waste disposal legislation is not an easy
task because the authorities are having difficulties in setting limits and
ensuring that they are adhered to. Nor has it yet been possible to break the
waste producers' resistance to disposing of the residues using the latest
technology as this entails very high costs for them.
Problematic organic industrial waste
The state environmental authority FEPAM has set up a hazardous
waste cadastre with the assistance of Technical Cooperation funds in which 383
large, medium and small-scale food and leather processing industries are
registered in greater Porto Alegre alone. In most of these industries, organic
waste from the production process is not being disposed of in an environmentally
For example, TANAC and SETA, the producers of organic leather
tanning agents, generate some 500,000 tons of acacia bark, a residue from tannin
extraction, each year and dump it near the factory grounds. In one very serious
case a dump was even established along a riverside in the outskirts of
Montenegro without sealing the foundations, and since 1990 the urban groundwater
there has been contaminated with lignin.
The state environmental authority FEPAM has declared the bark
extract dump a contaminated site. Since 1995 operators wishing to prolong their
operating licences have had to guarantee that residues from ongoing production
be disposed of according to the latest state of the art and in the long term
undertake to rehabilitate any contaminated sites generated in earlier production
The Vale do Cai region in Porto Alegre's immediate hinterland is
a traditional citrus fruit growing area. Full time and part time farmers
cultivate average cropping areas of 5 hectares, growing mandarines, lemons and
oranges using conventional methods. The PRORENDA project, an assistance
programme of German Technical Co-operation, is promoting small farmers in the
Harmonia region. It gave the first impulses for setting up co-operatives and
organising marketing in 1990.
In this context a group of mostly young citrus farmers decided
to turn to eco-farming and gradually switched over their fruit plantations to
less aggressive cropping methods without using mineral fertilisers and
pesticides. They quickly realised that for the new farming system to be
sustainable, artificial fertiliser must be replaced by high quality organic
A parallel survey revealed that large volumes of organic
residues from the agro-industries were dumped in the region. Pilot tests
demonstrated that the residues could be transformed into organic compost without
this requiring any large-scale technical input.
Organic waste composting project
The conditions were a favourable launching pad for the ECOCITRUS
concept. Industries, for their part, were faced with the problem of coping with
the new regulations to rehabilitate their contaminated sites and organise
appropriate disposal paths for everyday production waste. A group of committed
ecofarmers on the other hand, was working to obtain approval to use these waste
products as raw material for their composting process.
The ECOCITRUS group established itself as a company with the
goal of turning organic waste from the region into compost by aerobic
fermentation. The articles of association underlined the company's
non-profit-making goals. The final product - the compost - is to be distributed
amongst the share-holders, enabling them to save the high costs for mineral
The organic products obtained are expected to be an impulse for
the market. Initial surveys indicate that organic citrus fruits fetch a high
price on the Porto Alegre and Sao Paulo markets.
The group rented a 3.4 hectare site. The 20 shareholders
levelled and compacted the ground themselves, built a collecting tank for the
surface water and a sealed basin for the liquid fruit pulp, a component of the
composting process. To date, the company associates have covered the operating
costs by a monthly membership fee of 150 Real (approx. DM 230).
The GTZ-assisted "Environmental and Resource Protection FEPAM"
project provided consultancy to the farmers during the experimental phase.
Long-term and shortterm experts gave technical assistance on designing the
plantsite and optimising the composting process.
The composting process
The chief ingredients of the compost (expressed as m³ per
year) are: 50,000 m³ acacia bark, 6,000 m³ ash, 4,000 m³
charcoal, 3,000 m³ fruit pulp from orange juice manufacturing and 2,000
m³ paunch contents and other slaughterhouse waste. The organic wastes are
moistened with the fruit pulp, mixed and deposited in 1.5 m high triangular
stocks. Although the addition of fruit pulp with pH-value 5 hinders the
composting process at the beginning, this problem is remedied by adding ash from
burned acacia wood. The alkaline ash raises the pH-value to 6-7, which is
suitable for composting. Absorptive charcoal binds any unpleasant odours
generated when mixing the raw materials and during the composting process
itself. Thanks to the high proportion of bark sufficient structural material is
available, the oxygen supply is adequate and surplus heat is ventilated from the
centre of the stock.
These two processes (oxygen supply and heat removal) are vital
to composting and are supported by perforated plastic pipes sunk vertically into
the stock. Once prepared, the stocks are covered with a layer of acacia bark to
stop any unpleasant odours from escaping and to protect the composting material
from drying out or becoming too wet depending on the weather. When the stock
content is turned over, the moisture content can be regulated, if necessary, by
adding water from the rain collection tanks. The rotting process takes 6 - 9
months depending on the season.
The first results are very promising. The quality control of the
initial compost series gave the following values: moisture content 40 %, organic
content 40%, C/N ratio 10/1, nitrogen content 2%. The pure organic compost
obtained does not contain heavy metals or other pollutants.
ECOCITRUS is presently tackling the problem of reducing the
turn-around time of the material in the compost yard and ensuring that the high
volumes of material are processed better and more efficiently. 21,000 tons of
organic compost have been produced to date-enough to provide organic fertiliser
for 400 hectares of citrus