Sustainable Agricultural Waste Management: From a Holistic Approach to a Focus on Plastic Recycling

It is a sad, but a true fact, that waste is ubiquitous in the environment!  So what should we do about it? The message is sound and clear and comes from both inside and outside of the European Union, via the proposed and now widely known “waste hierarchy” (shown underneath). The pyramid mainly ranks the processes based on their ability to protect the environment and human health, alongside resource value recovery, with the tip of the pyramid presenting the most favorable option, and from there downwards we have options ranked from the most favorable to the least favorable one.

The waste generated in the agricultural sector is mostly of organic nature. According to the waste hierarchy organic waste should be recycled via composting (aerobic decomposition of organic matter), but environmental impact assessments have shown that other alternatives such as anaerobic digestion (where microorganisms decompose the organic matter in the absence of oxygen into biogas) can offer more benefits compared to composting even though it ranks lower in the waste hierarchy. This offers a fundamental insight; the waste hierarchy should not be followed blindly but used as a blueprint to identifying the right option for the management of waste following a holistic analysis of the environmental, economic, social and technical impacts as shown in the Table below. You can find out more here.

This becomes more evident when we look into the other types of waste materials generated in the agricultural sector, specifically plastics. Plastics or plastic-based materials are used in many different processes in the agricultural sector, such as: plastic films in low tunnels regulating the temperature and controlling other climatic conditions; mulch cover to retain humidity; plastic irrigation pipes that restrict the unnecessary use of water and/or nutrients; plastic reservoirs that can collect rain water; and plastic films used for silage storage protecting crops, just to name a few. Other plastic articles used in the agricultural sector include the boxes and plastic crates for crop collection-handling-transport, other irrigation system components (e.g. fittings and spray cones), tapes for keeping elevated the upper parts of the greenhouse plants, nets to darken the interior of the greenhouses or minimise the effects of hail.

All those plastic components and products serve a useful purpose, but once they reach the of their service life they become waste. The best option to manage these wastes is to retrieve them from the fields, sort them into flexible and rigid type and having them collected by a waste collection company that takes them to specialized facilities for treatment. Rigid plastics can go to sorting and reprocessing facilities where here they are sorted to different types (e.g. PET, HDPE, LDPE, PP) before being grinded, washed, decontaminated and turned into pellets. The secondary plastic materials generated via this treatment process can then be used again as recycled content in the manufacturing of new products i.e. bags, plastic lumbers and sidewalk pavers, a process widely known as downcycling, or cascading recycling process. In the case of films that are heavily contaminated and cannot be cleaned sufficiently, or other flexible plastic articles that cannot be reprocessed mechanically, the energy recovery process (following in order the recycling in the waste hierarchy) is a valuable alternative, recovering the calorific value of plastics.

All this sounds great right? But does this happen in reality? With only ca. 10% of agricultural plastics being currently recycled globally, it is safe to suggest that we have a long way ahead of us in moving towards a circular plastics economy in the agricultural sector. Most importantly, we need to revisit the waste hierarchy and begin our efforts to tackle agricultural waste management from the tip of the pyramid and move downwards according to the context and types of wastes generated. To that end a system of systems approach can help us understand the multi-faceted challenges that currently hamper progress in promoting sustainable circularity in the agricultural sector, and help us identify  which, and where changes are needed in the system to enable transformational change.

Dr. John N. Hahladakis
Chemical Engineer (M.Eng., double M.Sc., Ph.D.)
Asst. Professor
Center for Sustainable Development
Qatar University


The development of a sustainable food-production and -distribution system will be central to many of the world’s pressing challenges, including food poverty and hunger, climate change and pollution associated with agricultural practices. Even though substantial progress has been made in reducing the number of people dying from famine during the last century, in 2017, the UN officially declared that the spectre of famine had returned to Africa. The COVID-19 pandemic has further aggravated the situation as global supply chains became strained due to draconic lockdown measures and growing political tensions in certain countries. According to estimates from the IPCC’s Special Report on Climate Change and Land (2019), about 8.5% of all anthropogenic greenhouse gas (GHG) emissions come from the agricultural sector, with a further 14.5% resulting from land use change, i.e., primarily deforestation. The two biggest sources of greenhouse gas emissions from the agricultural sector are: (a) nitrous oxide emissions from agricultural soils; and (b) methane emissions from livestock and manures. In case you were wondering energy use accounts for less than 1.5% of total emissions of the agricultural sector.

Current practices in the livestock sector might also harbour a further health crisis. The World Resource institute estimates that it requires about nine kilojoules of animal feed to produce one kilojoule of poultry meat. The production of one kilojoule of protein from poultry, the most ‘climate-friendly’ type of animal agriculture, is responsible for 40 times as many GHG emissions as one kilojoule of protein from legumes. Moreover, approximately 80% of all antibiotics sold in the U.S. are currently used for the mass-production of animal products. This widespread (mis-)use significantly increases the risk of more strains of bacteria developing antibiotics resistance. The possible ensuing public health issues are frightening; it could deprive us of one of medicine’s most powerful tools, leading to huge social and economic costs. The costs of antibiotic resistant infections to the U.S. health care system alone sum up to tens of billions of US-dollars annually.

Could cultured meat be a potential solution to some of the aforementioned problems? Cultured meat is produced by in vitro cell cultures, using tissue engineering techniques similar to those used in regenerative medicine, rather than from slaughtered animals. Developments in this sector are still in their infancy, but progress has been rapid. This could cause an enormous disruption in the agricultural sector through a resource-efficient production of protein that could deliver many benefits including the eradication of famine. At least that is the general account provided by promoters of cultured meat. Currently many ambitious claims are being made around the potential benefits of the new technology, e.g. that cultured meat could significantly lower environmental impacts compared to conventional meat production, or that the use of cultured meat could help protect and restore biodiversity and halt the slaughtering of animals. It’s also been claimed that a large-scale adoption of cultured meat would not only significantly reduce the use of antibiotics in the meat production process, but that it could also significantly decrease the risk of the emergence and spread of animal-borne diseases like bird- and swine-flu. Further, the exposure to harmful substances such as pesticides and fungicides would be greatly reduced. But then again, what goes into the cultivated meat production process? What types of chemicals, and what’s the water and energy requirements to culture adequate amounts of cultured meat to cater for the growing demand for protein? Would it be ‘healthier’ than conventional meat, and, most importantly, would it be more sustainable?

For the time being, several of these points are largely speculative in nature and insufficient to draw any firm conclusions from; a systems approach could be the only way forward to determine the true benefits and to uncover potential hidden trade-offs that have to be taken into account by industry and policy makers alike.

Written by Dr. Norman Ebner, CRES strategic advisor