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Recycling urban waste on farmland

Recycling urban waste on farmland

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Member Since-29 Dec 2015


Let's start with a simple question. How can urban waste (in the form of sewage) be best disposed of? The manual collection and spread of night soil on farms adjacent to settlements have been a traditional method of disposing of the human excrement in sewage. This practice is still used in many developing countries ( Fahm 1980). Modern sewage systems, which date back to the 1950s in the UK, remove solid matter (sludge), from water-borne waste disposal systems that serve residential, industrial, and runoff. Roads and roofs are connected so that human excrement can be mixed with industrial and domestic waste products. Smith (1996) has compiled a lot of information on how to manage such sewage systems and treat and dispose of sludge. This is what we are not going to repeat here.


As the amount of sewage sludge that needs to be disposed of is increasing, sewage treatment facilities have been expanded. For example, approximately 12 million tonnes (dry material) of sewage sludge is produced each year in the Organization for Economic Cooperation and Development countries ( Linster 1991). There are many disposal options. Spreading crude sewage on areas that are not used for sewage "farms", spreading treated sewage on productive farmland, and incineration or landfill are just a few of the options. Because of its lower cost, dumping at sea has become a popular option in the UK. However, the European Union's Urban Wastewater Treatment Directive (91/271/EC), which prohibits member states from disposing sewage sludge at sea, was recently amended. Additionally, landfill operations in the UK are now subject to a tax.



Actor-network theory is a way to describe how intermediaries work in a network. In a narrative of translation within networks, intermediaries are particularly important. For example, acting away' refers to the ability of an external actor to enroll or mobilize an external’ actor into a network. This allows the researcher to describe how intermediaries work and explain why they fail to provide durability (stability) in the network. Law's Law 1992 terminology states that intermediaries play a crucial role in the mode of ordering' an actor-network. They use narratives, organizational forms, and materials to enroll actors to lengthen and stabilize a network. The actor-network theory narrative focuses on the construction, consolidation, and stabilization processes of an actor-network. This is because actors and intermediaries change over time, as well as the way they interact with one another. Sludge is rich in organic matter, as well as agriculturally useful nutrients such as organic and inorganic nitrogen, phosphorous, and potassium. 


Therefore, water companies represent sewage sludge not as an urban waste product that needs to be disposed of but as a useful source of fertilizer. For example, a typical application of sludge can provide recommended crop phosphate requirements for three to five years. The technical aspects of treating sewage sludge can have an impact on its chemical composition and thus influence the relationship between farmer and sludge. 

The nitrogen content in sewage sludge can change over time ( 1991). This requires farmers to make changes in their farming practices if they want to keep a close eye on the soil's nutrient status. Organic nitrogen is only absorbed by plants when it is converted into inorganic nitrogen in the soil. To achieve the same yields as when spreading manufactured inorganic fertilizer, it is necessary to use more sludge. Farmers may have additional difficulties controlling diffuse nitrate contamination from their farmland if this is done. This results in the fact that farmers who are enrolled in the actor-network (or not) are subject to a selection process based on their sludge characteristics and any necessary modifications to farming practices.

Three additional dangerous elements are also found in sewage sludge

1.Potential toxic elements (PTEs), in the form of heavy metals like arsenic and cadmium.


2.Pathogens, such as bacteria, viruses, and parasites.


3.Organic compounds are found in pesticides and detergents such as dioxins.

These elements can build up in the soil surface, and PTEs, as well as organic compounds, can enter the food chain through crops or indirectly by grazing livestock. For the Ministry of Agriculture, Fisheries, and Food ( MAFF, 1997), a recent study found that lambs grazed on cadmium-rich soils had accumulated it in their kidneys and livers, but not in their muscle tissues. PTEs can be found in industrial effluent. However, pathogens are more common in domestic and abattoir wastewater. Water companies have developed sewage treatment technologies to eliminate a lot of potentially hazardous sewage sludge. Scientists believe that organic compounds are mostly destroyed in sludge treatment, and new uses of organic compounds have been banned in the UK, as in the case with PCBs, since 1986. Water companies can present falling levels of PTEs within their sludge while minimizing the impact on toxic organic compounds or viruses ( Linster 1991, pages. 331-331). However, farmers are either unknowingly or knowingly risk-takers when spreading the sludge onto their land. Recent surveys of sewer sludge users ( Water Services Association 1996) have shown that many farmers are unaware of the nutrient contents of sludge and its monetary value as well as the dangers it presents.


The second component of the actor-network to recycle sewage sludge is Scientific Knowledge. It can be found in books, scientific papers, and technical documents. For example, the EU and national regulations have established permitted' soil contamination levels from PTEs and other dangerous elements. This includes PTEs as well as those affecting crop, livestock, and human uptake. These allowed levels are based on the recognition that spreading sewage waste into the soil can cause contamination to the soil and food chain. The EU COST68 program (1972-1990), which covered research projects from the USA, Canada, and Finland ( Linster 1991) has shown that certain PTEs, such as chromium and lead, remain immobile in soil and do not readily enter into water (as pollution) or into the biological cycle (the food chains). Some PTEs, like zinc and cadmium, can be absorbed by plants, which can lead to lower crop yields or contamination of the food chain. Plants have different levels of phytotoxicity. Common grasses and grains are more sensitive to PTEs than leafy veggies. The critical soil concentration thresholds (or safe limits') for PTE contamination vary depending on the type of soil. Acid soils are more retentive than those grown in crops, and scientific documents that contain this information have been an important intermediary in the circulation of the information within the actor-network.