One of the resources used by small farmers to fertilize their plantations is to use an organic compost obtained from urban garbage. Prepared by the sorting and composting plant using leftover food, fruit and vegetables and sold at far lower prices than the conventional fertilizers, the compost is particularly welcomed by those who grow greens. Although used since the 70’s, when the first units were installed in the country, to this date there is still no specific legislation establishing rules for the agricultural application of this product. When the quality is low, it can contaminate food with microorganisms like viruses and bacteria and cause serious environmental damage, such as the contamination of the soil and the water table by heavy metals and nitrates, substances that come in the main from human and animal feces.
Aware of the problem and knowing of the complaints from the farmers, amulti-institutional group of researchers decided to study urban composts in depth. Besides establishing a system for analysis that may serve for a future setting of standards for the product in Brazil, they created a pioneering system, built into a software capable of analyzing urban garbage compost. It advises which are the substances existing in each sample and provides indications about its use in farming.
The team is made up of researchers linked to the Brazilian Agricultural Research Corporation (Embrapa), the Piracicaba Engineering School (EEP), the Luiz de Queiroz College of Agriculture (Esalq), of the University of São Paulo (USP), the State University of Campinas (Unicamp), the University of Taubaté (Unitau) and the Campinas Agronomic Institute (IAC). A good part of the researches that served as a basis for developing the program was funded by FAPESP.
The recently created software, baptized as Intelligent System for Recommending the Use of Urban Garbage in Agriculture (Sirclua), will provide for a better control over the quality of the compost made in the country, and will assist rural producers in the suitable use of this organic manure, with every environmental security. Used up until now in the ambit of the university, the program is currently undergoing adaptation for use in the composting plants.
The first agreement for the commercial use of the system should be signed up with the Municipal Urbanizer (Urbanin the Portuguese acronym), the body that manages the collection of garbage, the sanitary landfill and the composting plant in the city of São José dos Campos (SP). The negotiations are well advanced. “We want to control our compost more closely, giving more security to the farmers who use it”, explains José Roberto Bráulio de Melo, the manager of Urban’s Waste Treatment Department.
Worth R$ 55,000, the contract provides for the supply of the program for analyzing the product obtained at the plant, and also for developing the standards for the use of urban garbage compost in parks and gardens and in agriculture. The composting plant in São José dos Campos produces 40 tons of compost a day, which is sold for R$ 20 the ton. “Our compost was the first and is perhaps the only one registered with the Ministry of Agriculture. We have never received any accusations of contamination by heavy metals”, explains Melo, a fact that is born out by the results of the research group.
Acceptable levels
“The Sirclua system is qualified to assess the quality of the compost, indicating whether or not it is within the minimum standards desirable for the cultivation of each farm product”, explains engineer agronomist Fábio César da Silva, a researcher with Embrapa Information Technology, and one of those responsible for creating and coordinating the system’s knowledge base. Among other things, the program assesses the physical and biological stabilization of the organic matter, the acceptable levels of heavy metals, the values for nitrogen, phosphorus and potassium present in the compost, and the efficiency of the use of nutrients in the crops. “The program also makes a recommendation for fertilizing, indicating the quantity to be used for a given soil or plant and, if applicable, whether it should be supplemented by chemical fertilizers. Accordingly, the team believes that they have established a standard procedure for the agricultural use of composting.”
According to the agronomist, the use of urban garbage compost in agriculture brings great benefits not only for the farmers, but for the environment as well. “With the use of urban garbage compost, the farmer enjoys great savings, because it replaces chemical fertilizers, which account for 30% to 40% of the cost of production, by organic manure, much cheaper”, says he. Furthermore, the compost is an excellent alternative for the recycling process. “It closes off the life cycle of the elements that make up the organic portion of garbage, which contributes towards relieving the pollutant burden of the sanitary landfills, doubling the useful life of these environments”, says Fábio Silva.
The advantage of getting the compost is that it frees the landfills from the problems that come from the organic part of the garbage, eliminating disagreeable situations, like the exhalation of odors, the formation of gases and leachate (a strong smelling liquid) that can generate a risk of environmental impact at the site, besides attracting and bringing about an increase in the population of rats, cockroaches, mosquitoes and other insects.
For the time being, Sirclua is qualified to issue recommendations on the use of the compost on ten different crops: rice, beans, sugarcane, triticale (a hybrid cereal between wheat and rye), corn, cassava, oats, lettuce, beet and chicory. All in the soil conditions of a major part of the state of São Paulo. “The quantity of the compost to be used by the farmer and the need or otherwise for a chemical supplement, with their respective quantities, are going to depend on the soil and the crop on which it is to be applied”, explains engineer agronomist Ronaldo Severiano Berton, a researcher at the Campinas Agronomic Institute (IAC), one of the members of the group. “With this tool, unprecedented in Brazil and perhaps in Latin America, we have created quality standards that may be used to format a legislation on composting in Brazil”, he says.
In the future, the researchers intention is to offer the program on the Internet, for any plant of rural producer to be able to access it free of charge. “To keep it up to date, the program is added to as and when knowledge about new applications in agriculture is generated”, says agricultural engineer Luiz Henrique Rodrigues, from the School of Agricultural Engineering at Unicamp, who coordinated the work of developing and implementing the software.
Composting in São Paulo city
The new program will be very useful in the places where the most problematical urban garbage composts found by the researchers are produced. “The two composting plants in the city of São Paulo, in the districts of Vila Leopoldina and São Mateus, and the one in the city in Santo André, for example, are not operating in a satisfactory manner. The rural producers in São Paulo’s green belt complain about the compost from the two São Paulo plants that supply them”, is Silva’s comment. “The compost and the precompost (the stage at which the product has not yet been duly cured, regarded merely as pretreated garbage) made by them has a large quantity of inert material, such as pieces of glass, plastic and ceramics. Even needles and dolls’ heads have already been found in it.”
A similar opinion is held by engineer agronomist José Carlos Chitolina, a retired professor from Esalq and a vice-director from the Piracicaba Engineering School. At the end of the 90’s, he did an exhaustive job of chemical characterization of the compost produced by the three units in São Paulo. “In our researches, we concluded that, compared with the standards defined by the legislation of several European countries, like Germany, Italy, France, Switzerland and Austria, the compost from the São Paulo plants had levels of heavy metals, such as copper, zinc, nickel, lead and, in particular, cadmium, above the acceptable levels, which ought to rule out the use of this material in agriculture”, says Chitolina. “But, unfortunately, it was sent to the São Paulo green belt without any environmental monitoring and without any control system.”
“The vegetables, for example, ought to use composts produced from selective garbage collection with levels of metal much lower than those shown in the samples collected.” In Chitolina’s work, the lead in the precompost at the Vila Leopoldina plant showed a level 20% higher than is acceptable. According to the researchers, greens ought to be given only composts coming from selectively collected garbage, because this succeeds in bringing down a lot the risk of contamination from microorganisms, and the levels of heavy metals become far lower.
Farmer Manuel dos Santos, former president of the Association of Producers of Vegetables of Arujá and Region (Apro-Horta), the owner of a rural property of 36,000 square meters where he grows vegetables, confirms the doubtful quality of the material sent by the plants. “The compost comes rough, with a lot of foreign material. After we receive it, we are obliged to carry out corrections and to finish composting, before applying it to the soil. Otherwise, as time goes by, the health of the workers would be jeopardized and the earth would become unusable, because of the great quantity of glass, plastic and heavy metals that keep accumulating in the field”, the farmer says.
Bad smell and mosquitoes
The quality of the precompost produced at the plant in Vila Leopoldina, located in the western region of the city of São Paulo, in actual fact, pretreated garbage, according to the researchers, is not the unit’s only problem. The strong odor exhaled from the installation and the proliferation of mosquitoes has for many years been causing dissatisfaction and generating protests from the residents in the vicinity. “The population suffers with the bad smell from the plant. There are complaints that the children at a school in the neighborhood even feel unwell during the lessons”, explains environmental prosecutor Geraldo Rangel, who intends to take out a public lawsuit asking for the plant to be closed.
“I have a report issued by the Environmental Sanitation Technology Company (Cetesb) attesting that the plant ought to bring its activities to a close, for operating too close to the community and for lacking the conditions for avoiding the bad smell. I am just waiting for other information concerning the risk of contamination from the precompost before starting the lawsuit”, explains the prosecutor. The research team was also invited by prosecutor Rangel to give an opinion on the situation of the quality of the compost and the need for corrective measures.
Another denouncement concerns the conditions of work at the plant. “They are awful”, says hemist Maria Gricia Grossi, a researcher with the Jorge Duprat Figueiredo Foundation for Security and Medicine at Work (Fundacentro), currently with the Secretariat for Environmental Quality in Human Settlements of the Ministry of the Environment, who drew up a technical report assessing the working conditions and environment at the composting unit in Vila Leopoldina.
The director of the city hall’s Urban Cleaning Department (Limpurb), Fabio Pierdomenico, defends himself from the accusations. For him, the problem of the odor should be resolved shortly. “Limpurb is now at the stage of concluding an addendum to the contract, which is going to make it possible to implant a system for neutralizing odors, among other measures, in the plan for mitigating environmental impacts. This plan also provides for the recovering of the bays where the recyclable materials are stored”, Pierdomenico explains. As to the accusations about the quality of the precompost produced at the plant, Limpurb’s director clarified that “it is difficult to take a stance, when there are no specific legal parameters for the organic portion and for the compost”.
He explains that, according to monthly laboratory tests carried out at the laboratories of Esalq, as well as in private laboratories, the precompost has levels of heavy metals and pathogenic bacteria below those set by the Environmental Sanitation Technology Company (Cetesb), by Embrapa and by the European Community. Be that as it may, it is possible to say that the new system for analysis and the software will be valuable for the production of a better quality compost in São Paulo and in the country, ensuring greater security in the food chain.
The Projects
1. Chemical Characterization of Urban Garbage Composts from Two Composting Plantsof Greater São Paulo (nº 97/14627-0); Modality Regular Research Grants Line; Coordinator José Carlos Chitolina – Esalq-USP; Investment R$ 10,375.00
2. Definition of Criteria for Applying Urban Garbage Compost to Sugarcane (nº 98/ 06439-2); Modality Regular Research Grants Line; Coordinator
Fábio César da Silva – Embrapa; Investment R$ 24,258.00 and US$ 1,661.00
