Introduction
The management of waste will probably be the most important environmental problem of the 21st Century. The industrialized societies generate different types of waste that require an environmental and economically acceptable solution, one of the greatest challenges both for the public administrations as well as for the private sector. For this reason, at the present time waste management activities are being fomented, prioritizing in this order the reduction, re-use, recycling, other forms of evaluation and, finally, the elimination, the least desirable.
Present situation
In recent years, as a result of the application of European Directive 91/271/CEE, the production of sewage sludge has been increased. In this directive the European Union committed itself to purifying its residual waters before 31 December 2000 in populations of over 15,000 people and before 31 December 2005 in smaller populations (between 2000 and 15,000 people).
At the present time, both European and national policies contemplate the possibility of re-using sewage sludge in agriculture. It is a very important source of organic matter and fertilization elements (mainly nitrogen and phosphorus), although its composition is extremely variable. In addition, this method allows these elements to be incorporated into the natural cycles of matter and energy, without altering the ecological balance and improving the much-needed organic matter content in our soils. The application of sewage sludge to the soil in the EU is regulated by the Council Directive of 12 June 1986 relating to the protection of the environment and, in particular, of the land, in the use of sewage sludge in agriculture, and was transposed to Spain by Royal Decree 1310/1990, of 29 October, by means of which the use of sewage sludge for agricultural application is regulated and whose development took place through the Order of 26 October 1993 on the use of sewage sludge for agricultural application. These policies restrict its application to the land on account of the presence of heavy metals in the sludge and soils, without specifying any other criteria as a fertilizing dose or forms of storage in the field.
Initially, this option for use is focused on the sewage sludge of municipal and agro-industrial waste water treatment plants (WWTP), because they have a similar composition and are in accordance with the pollutant limits required under the present legislation. Accordingly, the company that manages the WWTP must be committed to the generation of sewage sludge with the lowest metal levels possible, because the legislation being prepared is aimed at establishing more restrictive limits and requirements for agricultural application. Any sewage sludge that exceeds these concentration limits restricts its elimination to two alternatives: incineration and landfill, which are less viable from an economic, social and environmental point of view.
It is necessary to point out that agricultural application is the priority alternative as is indicated in the National Sewage Sludge Plan of WWTP 2001-2006: "As long sewage sludge complies with legal requirements, including those which might be established in the future (...) it is considered that the most sustainable option is the recycling of nutrients and organic matter by agricultural land application" (art. 1.3.). This plan estimated the production of sewage sludge from Municipal WWTP in Galicia at 90,000 tonnes dry matter/year and it is foreseen therein that 40% would go to agricultural use and soil conservation not-composting, 25 % for composting sewage sludge, 20 % to incineration with energy recovery, and 15 % to landfill.
Finally, it is possible to emphasize that two national regulations on the application of bio-solids exist; one is Royal Decree 824/2005, of 8 July, on fertilizing products, which governs the use of sewage sludge and other bio-solids in the elaboration of organic fertilizers and their commercialization, another is Directive 91/676/ EEC, transposed to Spanish legislation by the Royal Decree 261/1996, on the protection of the waters produced from the nitrates from agricultural sources, and on the basis of which the Code of Proper Agricultural Practice for Galicia was drawn up. In this Code, the main aspects relating to agricultural and livestock production which could give rise to nitrogen contamination are set out, and preventive measures and action are proposed.
In the Autonomous Community of Galicia, at the present time no rule exists that directly regulates the application of sewage sludge to the soil, but there does exist a guideline of the Consellería do Medio Rural (Department of the Rural Environment), used in agricultural land application, in which the application loading rate is established according to the levels of N and P in sewage sludge and other bio-solids, and according to the initial state of the soil and the crop to be grown. It also establishes storage regulations to avoid possible run-off and odour problems. This guideline will be approved in 2006.
Bio-solids
By using bio-solids in agriculture we take advantage of the fertilization capacity, already dealt with in various different articles on their advantages, but it is particularly important on account of the nitrogen contribution, mainly organic and of slow release, the contribution of phosphorous and other micronutrients, aside from being an important source of organic matter, improving the physical characteristics of soils and contributing nutrients to the crops.
In addition, the needs of chemical fertilizer are reduced and a CO2 fixation on the part of the crop takes place. In the event it were bio-energetic, fossil fuels are not used, and therefore on a global level the reserves of C in the soil are maintained or increased.
Having said this, all agricultural land applications must be adapted to the type of bio-solids, soil, crop, climate and to the system of management and treatment that be used.
Another important aspect in the use of bio-solids is pollutant concentration, both at the heavy metal level as well as any other type of non-degraded organic and synthetics chemicals in the process of residual water purification. In Galicia this industry is under-developed, and therefore the presence of these pollutants is lower in relation to other more industrialized autonomous communities and other more highly-developed European countries such as Germany. In a study carried out in the WWTP and dairy and food industry treatment plants in Galicia only one was over the limits of heavy metal content established by RD 1310/1990 for agricultural application. With respect to the microbiological quality of sewage sludge produced in our autonomous community, this is an aspect which is pending development, although our company - Agroamb -- with its treatment system is able to produce biosolids with the required standards of Biosolid Class A according to the EPA and in compliance with the microbiological limits set out in the draft directive on the biological treatment of bio-waste, this being an advanced treatment according to what is specified in the 3rd draft directive on the use of sewage sludge in the agricultural sector.
Agroamb contribution
Agroamb is a young company created in 2000 in the face of new necessities in the field of bio-solid management and their reuse, due to new environmental and water management policies. The company fundamentally manages sewage sludge, but works with every material also susceptible to safe recycling and with guarantees insofar as reuse is concerned, such as fertilizer or organic amendment.
We have developed a group of farmers of 2,500 ha. in Galicia, which is a database of information on farmland made up of approximately 220 farmers. We provide an integral advice and management service to provide the optimization of bio-solid use in their crops, mainly maize and grass production. In order to do so, has a wide range of agricultural machinery to give a greater quality service to the farmer; seeders, scatters, harvesters, for working and preparing the land, etc. and also its own laboratory. 85 % are centred in the province of Lugo, where an important part of cattle production in Galicia is concentrated. These plots are authorized and controlled by the Conselleria do Medio Rural of the Xunta of Galicia for fertilization and use of bio-solids, in direct collaboration with the Conselleria de Medio Ambiente.
With respect to bio-solid producers, Agroamb manages approximately 50,000 t per year of bio-solids, mainly sewage sludge, ashes from wood combustion and plant waste from the food and dairy industries (see graph).
Agroamb produces a fertilizing product from sewage sludge and other organic bio-products (plant waste, slurry, ashes...) in its treatment and transfer plant with an approximate surface area of 7000 m2 fed by renewable energy.
At the present time the company has several research projects in place in collaboration with various Galician universities and sector-related companies, among which are:
Future perspective
We are in a developing sector in Galicia but one with a lot of possibilities for the future. New European directives and regulations in our autonomous community on the use of bio-solids and sewage sludge in agriculture to increases control over this activity are pending approval. These regulations will increase society’s confidence with regard to the safety of using bio-solids for agricultural application. Sewage sludge production in Galicia is increasing as a result of the construction of new WWTP, in compliance the European directives on the treatment of residual waters and the greater exigency of the environmental regulations of the public administrations on the use of waters and the generation of waste and its treatment.
The development of the National Plan on Sewage Sludge is also pending, in which the guidelines to be followed with regard to valuating sewage sludge and its end destination are established, and in which important infrastructure and process investments are mentioned.
But we must not forget private sector investment in R+D+I (Research + Development + Innovation), very important for the study of bio-solids, their possible uses and treatment processes: anaerobic digestion, treatment with alkaline materials, composting, heat treatment, biogas, etc., always prioritizing agricultural use over elimination and studying different alternatives to make safer fertilizers with biosolids, and with an effective use from the environmental and agricultural point of view, and also to provide safety and confidence in their use for farmers and society in general.
Organization name: Agro Amb
Street address: Calzada das Gándaras, 11, Local Bajo Dcha.
City: Lugo
Postal code/ZIP: 27003
Country: Spain
Phone: +34 656 852 809
Fax: +34 982 240 534
E-mail: aamador@agroamb.com
Web: http://www.agroamb.com
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