Project

WasteReuse focuses on two significant environmental problems:

  • the uncontrolled disposal of agricultural wastes (olive oil mill wastes, wastes from the wine industry, etc) as well as, their uncontrolled use for crops/land fertilization.
  • the excess use of nutrients and natural resources (water, phosphoric minerals used for the production of fertilizers) and the potential to increase recycling of nutrients and water with sustainable use of treated (or potentially untreated) agricultural wastes

and aims :

  • to increase recycling of nutrients and water with sustainable use of treated (or potentially untreated) AW, and
  • to combine the up to now developed technologies in integrated methodologies for the sustainable recycling of waste nutrients and water in agriculture, considering:
    • the input needs of the main water-consuming crops cultivated in Mediterranean countries
    • the soil quality parameters that allow the use of this kind of wastes, and
    • the up to now accumulated knowledge regarding the sustainable use of AW in crop production across Europe and worldwide

Production of safe and high quality agricultural products as well as environmental protection are nowadays the focal point of public interest. There is a great necessity in developed countries to increase product quality, rather than quantity, due to the necessity of saving water and reducing food surplus, the increasing demand for strong respect and conservation of the environment and the fact that the vegetable market is no longer subject to needs of consumers but to their preferences.

Intensive farming systems use often excess amounts of water and fertilizers while nutrients are usually introduced through irrigation systems immediately after transplanting to produce strong healthy plants. This results in excessive use, e.g 20% to 30%, of fertilizers and almost doubles the amount of water actually needed by the crop. Apart from the high production cost and the low product competitiveness there are also serious environmental problems caused by these practices, such as useless water consumption, increased risk of desertification due to increased soil salinity, soil pollution/degradation, water pollution through leaching of the excess nutrients and soil biodiversity loss. Most of them have already been noticed in South Europe where a significant percentage of cultivated lands suffer from desertification mainly due to intensive agriculture, specific climatic conditions, wild fires and shortage of water.

The use of lower impact systems and the adoption of specific and/or innovative technologies for the prevention of resources consumption, while at the same time maintaining constant production levels to satisfy market demands, could lead to economic development at local/regional level as well as to environmental protection and improvement.

Vegetables, cereals and ornamentals production in Europe

Agriculture remains an important economic sector in the Mediterranean region. Total production of fruits and vegetables in the EU-15 (data for EU-27?) is about 115 million tons, which places it in the third place at world level after Asia (700 million tons) and Latin America and the Caribbean (127 million tons). Within Europe, the main fruit producer is Spain (32.3 %) followed by Italy (30.4 %), France (13.3 %) and Greece (9.7%). As regards vegetables the main producer is Italy (23.9 %) followed by Spain (20.9%) and France (14.6%). Regarding cereals, Spain and Italy belong to the 5 most productive European countries (France, Germany, United Kingdom, Spain and Italy) while according to FAO, 44.5% of the agricultural surface in Spain is devoted to cereals (FAO 2000). Moreover, the EU is the largest ornamentals and flowers producer worldwide (44% of the world production) while Italy holds the second place (15% of the total EU production) after Netherlands (32%).

Agricultural Wastes

In a strict sense the concept of agricultural waste refers to crops and pruning remains. These materials are characterized by high variability in water content (depending on crop development and harvest season), high organic matter content, changeable mineral fraction and high C/N ratio, depending on the residue nature and composition. The biodegradability of such residues depends on their relative content of easily biodegradable compounds (sugars, cellulose and hemicellulose) and more recalcitrant compounds such as lignin and polyphenols. Agricultural wastes may exhibit bad phytosanitary state as a result of the incidence of illness and plagues in the original crop, which should be taken into account when considering their treatment and management.

Agricultural wastes are characterized by the seasonality of their production and the need of rapid withdrawal from the field, avoiding interferences with other agricultural management options and preventing plagues or fire propagation.

In a more broad sense, the by-products of vegetal origin generated in food industries such as olive oil production, dry fruits elaboration, wine industry, etc. as well as, particular residues such as composts from mushroom cultivation, or substrates already utilized in greenhouse cultivations can be also considered as agricultural wastes. Agrarian wastes include also slurry and farmyard manure. Wastewaters are generated during washing, peeling or whitening processes and contain dissolved organic matter and suspended solids. Remaining pesticides, insects and juices can also be found.

The agricultural industry generates mainly liquid and solid residues with a high load of organic matter. The seasonal character of this type of industry means that high amounts of residues are generated in a short period of time. The amount of wastes generated as well as their characteristics depend on the type of crop processed.

The environmental impact of this kind of residues is considered significant and a sustainable management plan is required to avoid environmental degradation. Their inappropriate disposal causes soil and aquifer contamination as well as, emission of gases such as methane, ammonium and carbon dioxide to the atmosphere. The presence organic matter contained in these residues in superficial or groundwater can cause reduction of dissolved oxygen and fish death, production and emission of biogas, formation of a film of floating material and also eutrophication. When solid concentration in wastewaters is high, sediments can be formed in the bottom of the receiving waters where anaerobic degradation can take place with consequent production of bad odours. Water can also be contaminated by residual pesticides and other agrochemicals contained in wastewaters. In soils, wastes cause increase in N content which, further undergoes slow mineralization; only part of this N is used by crops and the rest is lixiviated contaminating groundwater with NO3– ions, which degrade aquatic environment and become harmful for human health.

Large quantities of AW are produced annually in the Mediterranean region. For example, it is estimated that cereal cultivation produces about 5.5-11.0 tons dry matter of residues per ha, residues from woody tree pruning constitute about 1.3-3.0 tons dry matter per ha, while the average total production of Olive Oil Mills Wastes ranges between 10 x106 and 12×106 m3 and occurs over a brief period of the year (November-March). These examples give an idea of the huge amount of residues generated and the necessity for developing sustainable management plans which will include recycling and re-use.

Recycling and Re-Use of Agricultural Wastes

Water resources shortage and environmental concerns have already led to wastewater reuse for irrigation. Most Mediterranean countries are arid or semi-arid with mostly seasonal and unevenly distributed precipitation. Due to the rapid development of irrigation and increased demand for domestic water supplies, conventional water resources have been seriously depleted. As a result, wastewater reclamation and reuse is increasingly being integrated in the planning and development of water resources in the Mediterranean region, particularly for irrigation.

The existence of guidelines is necessary for the planning and safe implementation of wastewater reuse for irrigation. Guidelines must also clearly promote the development of best practices. These do not need to be defined in great detail but must take into account important specific local conditions, such as the quality of reclaimed wastewater, the type of soil, the climate, the relevant crops and the local agricultural practices. However, the need for sharing a common rationale for developing wastewater reclamation and reuse standards on both sides of the Mediterranean is obvious The sustainable use of rain water and the re-use of dirty water will become an issue soon also for South Europe as it is already for North African and Middle East countries.

Water, soil and air quality protection requires proper management of organic waste derived from agricultural operations. Recycling of AW through land application for plant uptake and crop production is a traditional and proven waste utilization technique. If properly done, is an environmentally sound method of waste management resulting also in economical benefits due to the reduction of commercial fertilizers use.

Since agricultural wastes are rich in inorganic nutrients (micro- and macro- elements) and organic matter, recycling of this type of wastes in agriculture would contribute to

  • significant reduction of harmful wastes disposed in the environment
  • recycling of elements and water in agriculture which in turn, will reduce production cost and contribute to the increase in European products competiveness and profits
  • protection of renewable and non-renewable resources (soil, aquatic bodies, phosphoric minerals) through elements recycling

However, if land distribution is planned (e.g. for irrigation) the organic load and the toxic substances (e.g. polyphenols) present in treated or untreated wastes should not be the only issues of concern. Specific care should be taken also for inorganic constituents and especially for K, Cl–, NO3–, SO42-, P, Mg, Fe, Zn and others, since the very high concentrations disposed on soil change its quality properties drastically, while the concentrations of the inorganic soil constituents (especially K, P, Fe, Cu, SO22-) and the electrical conductivity remain high even many years after the last disposal1.

This was also confirmed from the implementation of the on-going LIFE+07 ENV/GR/000280 project “Strategies to improve and protect soil quality from the disposal of olive oil mills in the Mediterranean-PROSODOL” (http://www.prosodol.gr). It was found that soil properties are strongly affected by the direct disposal of Olive Oil Mills Wastes on soil as well as, in unprotected evaporation ponds, mainly through waste transfer and leaching. Soils that accept OOMW are rich in organic matter, inorganic nutrients as well as in polyphenols.1,2 Although organic matter and nutrients could be beneficial for soil fertility and plant growth, potential serious soil degradation should always be considered due to very high concentrations of inorganic elements and polyphenols, sometimes near or above thresholds. Moreover, the addition of the insufficiently stable organic matter present in wastes, although it leads to the general increase in soil organic matter, may induce a number of negative effects on soil properties and plant growth, such as increase in mineralization rate of native organic carbon, induction of anaerobic conditions and release of phytotoxic substances that may have negative effects on plant growth.3.4

Previous studies and projects dedicated to the development of AW treatment technologies focused mainly on the reduction of the wastes organic load (COD, BOD) and on the reduction or the recovery of valuable substances, such as polyphenols from OOMW, which are indeed harmful for the environment.. However, by introducing inorganic nutrients in the picture, the puzzle of what may cause soil degradation at AW disposal areas, could be completed, and it is now possible to evaluate the up to now developed technologies for AW treatment regarding the quality characteristics of treated wastes and thus, their suitability for agricultural use.

Although some of the up to now developed technologies for AW treatment have studied the effects of treated wastes on growth and yield parameters of a few crops, it should be noticed that in order AW to be used safely in agriculture, specific cultivation practices should be developed after detailed study of

  • the effect of AW on plant growth and yield quality characteristics
  • water and nutrients demand of the specific crops
  • the effect of AW on soil properties
  • the soil-climatic relations
  • the environmental conditions

thus, WASTEREUSE proposes:

the development of new, alternative agricultural practices with the use of treated (or potentially untreated) AW by considering all the above factors as significant parameters, that affect, apart from the production itself, the quality of soil, water, and air.

 References

1. Kavvadias, V., Doula, M., Komnitsas, K., Liakopoulou, N. Disposal of olive oil mill wastes in evaporation ponds : Effects on soil properties. J. Hazardous Mater. 182, (2010), 144-155.

2. Doula M., Kavvadias, V. Theocharopoulos S., Kouloumbis P., Ikonomou, D., Arapoglou D. Environmental impacts relative to soil quality caused from the disposal of olive oil mills’ wastes. Case study: A municipality in Crete, Greece. Proceedings of AMIREG 2009: Advances in Resources & Hazardous Wastes Management towards Sustainable Development, 3rd International Conference, 7-7 September, Athens, Greece, pp. 84

3. Cereti, C.F., Rossini, F., Federici, F., Quaratino, D., Vassilev, N., Fenice, M. Reuse of microbially treated olive mill wastewater as fertilizer for wheat (Triticum durum Desf.). Biosour. Technol. 91 (2004), 135-140.

4. Komilis, D.P. Karatzas, E., Halvadakis, C.P. The effect of olive mill wastewater on seed germination after various pre-treatment techniques. J. Environ. Manag. 74 (2005), 339-348.