Waste Disposal Methods: Perspectives for Africa

Waste disposal methods vary from city to city, state to state and region to region. It equally depends on the kind and type of waste generated. In determining the disposal method that a city or nation should adopt, some factors like type, kind, quantity, frequency, and forms of waste need to be considered.

For the purpose of this article, we will look at the three common waste disposal methods and the kind of waste they accept.

Open Dumping/Burning

This is the crudest means of disposing of waste and it is mostly practiced in rural areas, semi-urban settlements, and undeveloped urban areas. For open dumping or open burning, every type and form of waste (including household waste, hazardous wastes, tires, batteries, chemicals) is dumped in an open area within a community or outside different homes in a community and same being set on fire after a number of days or when the waste generator or community feels it should be burnt.

There is no gainsaying that the negative health and environmental impact of such practice are huge only if the propagators know better.

Controlled Dumping

This is apparent in most States in Nigeria, if not all and some cities in Africa like Mozambique, Ghana, Kenya, Cameroon, to mention but a few. It is a method of disposing of all kinds of waste in a designated area of land by waste collectors and it is usually controlled by the State or City Government.

Opening burning of trash is a common practice across Africa

Controlled dumps are commonly found in urban areas and because they are managed by the government, some dumps do have certain features of a landfill like tenure of usage, basic record keeping, waste covering, etc. Many cities in Nigeria confuse the practice of controlled dumping as landfilling but this not so because a landfill involves engineering design, planning, and operation.

Sanitary Landfill

A sanitary landfill is arguably the most desired waste management option in reducing or eliminating public health hazards and environmental pollution. The landfill is the final disposal site for all forms and types of waste after the recyclable materials must have been separated for other usages and other biodegradables have been extracted from the waste for use as compost, heat, or energy; or after incineration. These extractions can be done at household level or Material Recovery Facilities (MRFs) operated by the government or private individuals.

As desirable as a landfill is, so many factors need to be put into consideration in its siting and operation plus it requires a huge investment in construction and operation. Some of these factors include but not limited to distance from the residential area, proximity to water bodies, water-table level of the area the landfill is to be sited, earth material availability, and access road.

Note: The original version of the article was published on Waste Watch Africa website at this link.

Solid Waste Management in Morocco

solid_waste_moroccoSolid waste management is one of the major environmental problems threatening the Kingdom of Morocco. More than 5 million tons of solid waste is generated across the country with annual waste generation growth rate touching 3 percent. The proper disposal of municipal solid waste in Morocco is exemplified by major deficiencies such as lack of proper infrastructure and suitable funding in areas outside of major cities.

According to the World Bank, it was reported that before a recent reform in 2008 “only 70 percent of urban wastes was collected and less than 10 percent of collected waste was being disposed of in an environmentally and socially acceptable manner. There were 300 uncontrolled dumpsites, and about 3,500 waste-pickers, of which 10 percent were children, were living on and around these open dumpsites.”

It is not uncommon to see trash burning as a means of solid waste disposal in Morocco.  Currently, the municipal waste stream is disposed of in a reckless and unsustainable manner which has major effects on public health and the environment.  The lack of waste management infrastructure leads to burning of trash as a form of inexpensive waste disposal.  Unfortunately, the major health effects of burning trash are either widely unknown or grossly under-estimated to the vast majority of the population in Morocco.

The good news about the future of Morocco’s MSW management is that the World Bank has allocated $271.3 million to the Moroccan government to develop a municipal waste management plan.  The plan’s details include restoring around 80 landfill sites, improving trash pickup services, and increasing recycling by 20%, all by the year 2020. While this reform is expected to do wonders for the urban population one can only hope the benefits of this reform trickle down to the 43% of the Moroccan population living in rural areas, like those who are living in my village.

Needless to say, even with Morocco’s movement toward a safer and more environmentally friendly MSW management system there is still an enormous population of people including children and the elderly who this reform will overlook.   Until more is done, including funding initiatives and an increase in education, these people will continue to be exposed to hazardous living conditions because of unsuitable funding, infrastructure and education.

Waste Management Outlook for India

Waste management crisis in India should be approached holistically; while planning for long term solutions, focus on addressing the immediate problems should be maintained. National and local governments should work with their partners to promote source separation, achieve higher percentages of recycling and produce high quality compost from organics. While this is being achieved and recycling is increased, provisions should be made to handle the non-recyclable wastes that are being generated and will continue to be generated in the future.

Recycling, composting and waste-to-energy are all integral parts of the waste disposal solution and they are complementary to each other; none of them can solve India’s waste crisis alone. Any technology should be considered as a means to address public priorities, but not as an end goal in itself. Finally, discussion on waste management should consider what technology can be used, to what extent in solving the bigger problem and within what timeframe.

Experts believe India will have more than nine waste-to-energy projects in different cities across India in the next three years, which will help alleviate the situation to a great extent. However, since waste-to-energy projects are designed to replace landfills, they also tend to displace informal settlements on the landfills. Here, governments should welcome discussions with local communities and harbor the informal recycling community by integrating it into the overall waste management system to make sure they do not lose their rights for the rest of the city’s residents.

This is important from a utilitarian perspective too, because in case of emergency situations like those in Bengaluru, Kerala, and elsewhere, the informal recycling community might be the only existing tool to mitigate damage due to improper waste management as opposed to infrastructure projects which take more than one year for completion and public awareness programs which take decades to show significant results.

Involvement of informal recycling community is vital for the success of any SWM program in India

Indian policy makers and municipal officials should utilize this opportunity, created by improper waste management examples across India, to make adjustments to the existing MSW Rules 2000, and design a concrete national policy based on public needs and backed by science. If this chance passes without a strong national framework to improve waste management, the conditions in today’s New Delhi, Bengaluru, Thiruvananthapuram, Kolkata, Mumbai, Chennai, Coimbatore and Srinagar will arise in many more cities as various forcing factors converge. This is what will lead to a solid waste management crisis affecting large populations of urban Indians.

The Indian Judiciary proved to be the most effective platform for the public to influence government action. The majority of local and national government activity towards improving municipal solid waste management is the result of direct public action, funneled through High Courts in each state, and the Supreme Court. In a recent case (Nov 2012), a slew of PILs led the High Court of Karnataka to threaten to supersede its state capital Bengaluru’s elected municipal council, and its dissolution, if it hinders efforts to improve waste management in the city.

In another case in the state of Haryana, two senior officials in its urban development board faced prosecution in its High Court for dumping waste illegally near suburbs. India’s strong and independent judiciary is expected to play an increasing role in waste management in the future, but it cannot bring about the required change without the aid of a comprehensive national policy.

Note: Acknowledgements will be published in the full report “Observations from India’s Crisis” on wtert.org and blog.wtert.org

A Primer on Waste-to-Energy

Waste-to-Energy is the use of modern combustion and biochemical technologies to recover energy, usually in the form of electricity and steam, from urban wastes. These new technologies can reduce the volume of the original waste by 90%, depending upon composition and use of outputs.

Energy is the driving force for development in all countries of the world. The increasing clamor for energy and satisfying it with a combination of conventional and renewable resources is a big challenge. Accompanying energy problems in different parts of the world, another problem that is assuming critical proportions is that of urban waste accumulation.

The quantity of waste produced all over the world amounted to more than 12 billion tonnes in 2006, with estimates of up to 13 billion tonnes in 2011. The rapid increase in population coupled with changing lifestyle and consumption patterns is expected to result in an exponential increase in waste generation of upto 18 billion tonnes by year 2020.

Waste generation rates are affected by socio-economic development, degree of industrialization, and climate. Generally, the greater the economic prosperity and the higher percentage of urban population, the greater the amount of solid waste produced. Reduction in the volume and mass of solid waste is a crucial issue especially in the light of limited availability of final disposal sites in many parts of the world. Millions of tonnes of household wastes are generated each year with the vast majority disposed of in open fields or burnt wantonly.

The main categories of waste-to-energy technologies are physical technologies, which process waste to make it more useful as fuel; thermal technologies, which can yield heat, fuel oil, or syngas from both organic and inorganic wastes; and biological technologies, in which bacterial fermentation is used to digest organic wastes to yield fuel.

The three principal methods of thermochemical conversion are combustion in excess air, gasification in reduced air, and pyrolysis in the absence of air. The most common technique for producing both heat and electrical energy from wastes is direct combustion. Combined heat and power (CHP) or cogeneration systems, ranging from small-scale technology to large grid-connected facilities, provide significantly higher efficiencies than systems that only generate electricity.

Biochemical processes, like anaerobic digestion, can also produce clean energy in the form of biogas which can be converted to power and heat using a gas engine. In addition, wastes can also yield liquid fuels, such as cellulosic ethanol, which can be used to replace petroleum-based fuels. Cellulosic ethanol can be produced from grasses, wood chips and agricultural residues by biochemical route using heat, pressure, chemicals and enzymes to unlock the sugars in biomass wastes.

Waste-to-energy plants offer two important benefits of environmentally safe waste management and disposal, as well as the generation of clean electric power.  The growing use of waste-to-energy as a method to dispose of solid and liquid wastes and generate power has greatly reduced environmental impacts of municipal solid waste management, including emissions of greenhouse gases.

Biorefinery Prospects in India

India has a tremendous biomass potential which could easily be relied upon to fulfil most of our energy needs. An estimated 50 MMT (million metric tonnes) of liquid fuels are consumed annually in India, but with the actual biomass potential and its full utilization, India is capable of generating almost double that amount per annum. These biomass estimates only constitute the crop residues available in the country and essentially the second-generation fuels since the use of first-generation crop bases fuels in such food-starved nations is a criminal thought.

Existing Technologies

Currently, there are various technologies available to process such crop residues and generate value products from them. However, essentially, they all revolve around two main kinds of processes, either biochemical or thermal.

The biochemical process involves application of aerobic/anaerobic digestion for the production of biogas; or fermentation, which results in the generation of ethanol. Both these products could be subsequently treated chemically and through trans-esterification process, leading to production of biodiesel.

Alternatively, the thermochemical processes involve either the combustion, gasification or pyrolysis techniques, which produces heat, energy-rich gas and liquid fuels respectively. These products can be used as such, or could be further processed to generate high quality biofuels or chemicals.

The Need

The estimated organized energy breakup for India is 40 percent each for domestic and transport sectors and 20 percent for the industrial sectors. The current share of crude oil and gases is nearly 90 percent for the primary and transport sectors and the remaining 10 percent for the generation of industrial chemicals. The escalating prices of crude oil in the international market and the resulting concern over energy security, has lead developing nations to explore alternative and cheap sources of energy to meet the growing energy demand. One of the promising solution for agrarian economies is Biorefinery.

The Concept

Biorefinery is analogous to the traditional petroleum refineries employing fractional distillation process for obtaining different fractions or components from the same raw material, i.e. the crude oil. Biorefinery involve the integration of different biomass treatment and processing methods into one system, which results in the production of different components from the same biomass.  This makes the entire chain more viable economically and also reduces the waste generated.

Typical Model of a Biorefinery

The outcome ranges from high-volume, low-energy content liquid fuels, which could serve the transportation industry needs, to the low-volume but high-value chemicals, which could add to the feasibility of such a project. Steam and heat generated in the process could be utilized for meeting process heat requirements. By-products like chemicals, fertilizers, pharmaceuticals, polymers etc are also obtained which provide additional revenue streams.

Benefits

Biorefineries can help in utilizing the optimum energy potential of organic wastes and may also resolve the problems of waste management and GHGs emissions. Wastes can be converted, through appropriate enzymatic/chemical treatment, into either gaseous or liquid fuels. The pre-treatment processes involved in biorefining generate products like paper-pulp, HFCS, solvents, acetate, resins, laminates, adhesives, flavour chemicals, activated carbon, fuel enhancers, undigested sugars etc. which generally remain untapped in the traditional processes. The suitability of this process is further enhanced from the fact that it can utilize a variety of biomass resources, whether plant-derived or animal-derived.

Applicability

The concept of biorefinery is still in early stages at most places in the world. Problems like raw material availability, feasibility in product supply chain, scalability of the model are hampering its development at commercial-scales. The National Renewable Energy Laboratory (NREL) of USA is leading the front in biorefinery research with path-breaking discoveries and inventions. Although the technology is still in nascent stages, but it holds the key to the optimum utilization of wastes and natural resources that humans have always tried to achieve. The onus now lies on governments and corporate to incentivize or finance the research and development in this field.

Waste Management in Global North and Global South

Waste management is highly context specific. Therefore it is important to distinguish between the conditions in the Global North and the Global South. Recent ILO figures suggest that 24 million people around the world are involved in the informal waste recycling sector, 80% of whom are waste pickers. Some estimates say that 1% of urban population in developing countries makes their primary household income through informal sector waste management activities.  In Latin America alone, 4-5 million waste pickers earn their livelihood by being a part of the global recyclables supply chain.

Municipal budgets in the Global South are often limited and only a small percentage of that budget is assigned to waste management as compared to other municipal services. In the Global North waste management is recognized as a necessary public good and there is a greater willingness to pay for this service. Solid waste management (e.g. waste collection, transportation and recycling) is generally more labour intensive than in North America and Europe.

Urbanization in the Global South is often haphazard and unplanned; creating pockets of high and low income neighbourhoods. This creates logistical issues for the waste management service provision limiting options for viable waste collection and transportation. It is often the informal sector that steps in to fill this service gap.

The maturity and strength of the legal framework differs between the Global South and Global North. In North America and Europe the legal framework of waste management actively promotes and provides incentives for waste reduction, reuse and recovery whereas, despite recent developments in some countries, in Latin America legal frameworks remain focused upon mixed waste collection, transportation and disposal.

Recycling rates in Argentina are at 11% of the total waste stream with 95% of this material is recovered by the informal sector. This situation is replicated in many other countries. The informal sector recovers between 50% (e.g. Mexico) and 90% (e.g. Nicaragua) of the waste recovered and in the different countries of the region. Resource recovery and recycling is driven by market conditions. Materials that have a value are diverted from landfill through an informal network of recyclers and waste collectors.

The composition of waste is also very different in the Global South where organic waste is a much larger percentage of the waste stream. Because of the high percentage of organics in the waste stream in many cities in the Global South, innovations in decentralised composting and small scale biogas have been seen across the Global South (particularly in India) and can be used effectively by the informal sector, making a zero waste future a real possibility.

Role of Informal Recycling Sector

The informal sector can be highly effective at collecting and diverting garbage from landfill. When empowered with a facilitating legal framework, and collectively organized, the informal sector can be a key part of a sustainable resource recovery system. Using people power to increase recycling and diversion rates decreases the need for expensive, fixed, high technology solutions.

Understanding that the context for waste management is different between the Global North and Global South, and even in different areas within a city or region, means that no two situations will be the same. However, if there is one principle to follow it may well be to consider the context and look for the simplest solution. The greenest cities of the future may well be those that use flexible, adaptable solutions and maximize the work that the informal sector is already doing.

Note: This excerpt is being published with the permission of our collaborative partner Be Waste Wise. The original excerpt and its video recording can be found at this link

Recycling Outlook for Latin America

Latin America has one of the highest rates of urbanization in the world (80% urban population). By 2050, 90% of Latin America’s population will live in urban areas. This high rate of urbanization coupled with the global economic crisis has resulted in a waste management crisis. Municipalities find themselves unable to keep up with providing services and infrastructure to the urban populations.

Some cities in Latin America are facing this challenge by integrating the informal sector recyclers who are already active in their cities into the municipal solid waste management systems. In many cities, these “recicladores”, “cartoneros” or “catadores” (a few of the many names used for these workers in the region) are responsible for up to 90% of the recyclable waste recovered from the waste stream. Their work reduces municipal waste transportation costs, increases landfill lifetimes and supports the recycling chain throughout the region.

State of the Affairs

Every location presents its own challenges–there is no one-size-fits-all solution for integrated solid waste management systems–but relevant lessons can be drawn from both failed attempts and successful examples of informal sector integration in recycling systems in Latin America.

There are often two very different contexts within cities. In low-income neighborhoods waste collection services are often not provided and individuals and families accumulate and then sell their recyclables for additional income. In contrast, residents in high income neighborhoods do receive a waste collection service and their motivation for recycling is often related to greater levels of environmental awareness. It is important to consider these differences when designing waste management solutions.

Imported systems, and even locally derived systems based on examples from the Global North, generally focus on only one waste management scenario, making it difficult to manage the multiple competing scenarios in many cities in Latin America. There is often a bias towards the automation of waste management services, with the application of the high technology solutions used in the Global North. Regardless of the practicality or scientific evidence against certain high tech solutions, these are often sought after, thought to raise the bar of the city, to make it appear more sophisticated and modern. This leads to a misconception that working with informal sector is a step backwards in terms of urban development and modernization.

Conflicts between private waste management companies, the municipality and informal recyclers are common. The waste management companies do not want pickers on the landfill and wastepickers then go to the municipality for help. However, municipalities usually have very little experience to support the integration of formal and informal waste sectors. There are opportunities for new systems to emerge within this conflict. For example, during a similar conflict in Mexicali, Mundo Sustentable, with the help of Danone, intervened to help a private company work with the informal waste sector and improve recycling rates.

The Way Forward

In Latin America, there is a great opportunity to increase recycling rates by using labour-intensive solutions, which create jobs and support the development of a better urban environment in the cities. Municipal governments should be an integral part of these processes as they are usually responsible for solid waste management at local level. The key to catalyzing informal recycling sector integration will be the development and dissemination of successful examples.

Informal recyclers provide important a range of services to municipalities (such as waste collection and recovery in communities that would not otherwise have access to them), as well as cost savings (for example, the extension of landfill life and reduced transport costs), yet are rarely compensated for these benefits. Informal recyclers further form the foundation of an entire recycling supply chain, which ultimately benefits formal businesses, and often aliment entire local economies.

Challenges to Overcome

Municipal governments are often hesitant to work with informal actors, who are frequently seen as an unknown quantity. Yet often in the process of working and developing relations with informal recycler groups, their concerns diminish and they may actually exhibit enthusiasm. Likewise, the recyclers may gain in confidence and professionalism in their experience of formalization.

One major challenge facing efforts to integrate the informal sector in developing countries is the desire of some local governments to adopt technological solutions that appear more “modern.” In much of Latin America, however, low-cost, low-tech solutions tend to be more viable and sustainable.

The main difference between Latin America and the countries of the Global North is that solid waste management is a labor intensive system. It is made up of workers and hence has an important social component. The ILO estimated there is 24 million of people working in the global recycling supply chain, but those at the bottom of the pyramid, the wastepickers, make up 80%. They remain the lowest paid even though they make an enormous contribution to their cities.

It is important to understand that highly sophisticated, high technology systems are not required for effective resource recovery. In many cities in Latin America between 80-90% of everything that is recycled is recovered by the informal recycling sector.

Despite the fact that there is little or no public investment in waste management or recycling infrastructure, cities with an active informal sector reach twice the rate of fully formalized municipal solid waste management systems. As an example, the recycling rate is 60% in Cairo, while in Rotterdam (and other cities in the Global North) recycling levels only reach 30%, even with a high public investment in the system (UN Habitat, 2010).

When designing infrastructure and waste management systems we must consider not only the waste management and resource recovery needs but also the social side of the system. In order to be effective, efforts to upgrade waste management services should go hand in hand with efforts to formalise and integrate the informal sector.

Bogota – A Success Story

An example of a recent success story is that after 27 years of struggle, the waste pickers in Bogota, Colombia have managed to change the government’s outlook on their work and their existence. They are now included in the system and are paid per tonne of waste collected, just like any other private sector collection and waste management company would be. They have become recognized as public service providers, acknowledged for their contribution to the environment and public health of the city.

The key challenge is to be much more creative and understand that in order to improve the working conditions of waste pickers and in order to increase recycling rates, we don’t need high technology. We need a systemic approach and this can be very simple sometimes infrastructure as simple as a roof [on a sorting area] can be effective in improving working conditions.

Note: This excerpt is being published with the permission of our collaborative partner Be Waste Wise. The original excerpt and its video recording can be found at this link

Agricultural Wastes in the Middle East

Agriculture plays an important role in the economies of most of the countries in the Middle East.  The contribution of the agricultural sector to the overall economy varies significantly among countries in the region, ranging, for example, from about 3.2 percent in Saudi Arabia to 13.4 percent in Egypt.  Large scale irrigation is expanding, enabling intensive production of high value cash and export crops, including fruits, vegetables, cereals, and sugar.

The term ‘crop residues’ covers the whole range of biomass produced as by-products from growing and processing crops. Crop residues encompasses all agricultural wastes such as bagasse, straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. Wheat and barley are the major staple crops grown in the Middle East region. In addition, significant quantities of rice, maize, lentils, chickpeas, vegetables and fruits are produced throughout the region, mainly in Egypt, Syria, Saudi Arabia and Jordan.

Date palm is one of the principal agricultural products in the arid and semi-arid region of the world, especially Middle East and North Africa (MENA) region. The Arab world has more than 84 million date palm trees with the majority in Egypt, Iraq, Saudi Arabia, Iran, Algeria, Morocco, Tunisia and United Arab Emirates. Date palm trees produce huge amount of agricultural wastes in the form of dry leaves, stems, pits, seeds etc. A typical date tree can generate as much as 20 kilograms of dry leaves per annum while date pits account for almost 10 percent of date fruits. Some studies have reported that Saudi Arabia alone generates more than 200,000 tons of date palm biomass each year.

In Egypt, crop residues are considered to be the most important and traditional source of domestic fuel in rural areas. These crop residues are by-products of common crops such as cotton, wheat, maize and rice. The total amount of residues reaches about 16 million tons of dry matter per year. Cotton residues represent about 9% of the total amount of residues. These are materials comprising mainly cotton stalks, which present a disposal problem. The area of cotton crop cultivation accounts for about 5% of the cultivated area in Egypt.

A cotton field in Egypt

Large quantities of crop residues are produced annually in the Middle East, and are vastly underutilised. Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. These residues could be processed into liquid fuels or thermochemical processed to produce electricity and heat in rural areas. Energy crops, such as Jatropha, can be successfully grown in arid regions for biodiesel production. Infact, Jatropha is already grown at limited scale in some Middle East countries and tremendous potential exists for its commercial exploitation.

A wide range of thermal and biochemical technologies exists to convert the energy stored in agricultural wastes into useful forms of energy. Thermochemical conversion technologies like combustion, gasification and pyrolysis can yield steam, syngas, bio oil etc. On the other hand, the high volatile solids content in agro wastes can be transformed into biogas in anaerobic digestion plants, possibly by codigestion with MSW, sewage sludge, animal wastes and/and food wastes. The cellulosic content in agricultural residues can be transformed into biofuel (bioethanol) by making use of the fermentation process. In addition, the highly organic nature of agricultural wastes makes it highly suitable for compost production which can be used to replace chemical fertilizers in agricultural farms. Thus, abundance of agro residues in the Middle East can catalyze the development of biomass energy sector in the region.

Date Palm as Biomass Resource

date-wastesDate palm is one of the principal agricultural products in the arid and semi-arid region of the world, especially Middle East and North Africa (MENA) region. There are more than 120 million date palm trees worldwide yielding several million tons of dates per year, apart from secondary products including palm midribs, leaves, stems, fronds and coir. The Arab world has more than 84 million date palm trees with the majority in Egypt, Iraq, Saudi Arabia, Iran, Algeria, Morocco, Tunisia and United Arab Emirates.

Egypt is the world’s largest date producer with annual production of 1.47 million tons of dates in 2012 which accounted for almost one-fifth of global production. Saudi Arabia has more than 23 millions date palm trees, which produce about 1 million tons of dates per year. Date palm trees produce huge amount of agricultural wastes in the form of dry leaves, stems, pits, seeds etc. A typical date tree can generate as much as 20 kilograms of dry leaves per annum while date pits account for almost 10 percent of date fruits. Some studies have reported that Saudi Arabia alone generates more than 200,000 tons of date palm biomass each year.

Date palm is considered a renewable natural resource because it can be replaced in a relatively short period of time. It takes 4 to 8 years for date palms to bear fruit after planting, and 7 to 10 years to produce viable yields for commercial harvest. Usually date palm wastes are burned in farms or disposed in landfills which cause environmental pollution in dates-producing nations. In countries like Iraq and Egypt, a small portion of palm biomass in used in making animal feed.

The major constituents of date palm biomass are cellulose, hemicelluloses and lignin. In addition, date palm has high volatile solids content and low moisture content. These factors make date biomass an excellent waste-to-energy resource in the MENA region. A wide range of thermal and biochemical technologies exists to convert the energy stored in date palm biomass to useful forms of energy. The low moisture content in palm wastes makes it well-suited to thermochemical conversion technologies like combustion, gasification and pyrolysis which may yield steam, syngas, bio oil etc. On the other hand, the high volatile solids content in date palm biomass indicates its potential towards biogas production in anaerobic digestion plants, possibly by codigestion with sewage sludge, animal wastes and/and food wastes. The cellulosic content in date palm wastes can be transformed into biofuel (bioethanol) by making use of the fermentation process. The highly organic nature of date palm biomass makes it highly suitable for compost production which can be used to replace chemical fertilizers in date palm plantations. Thus, abundance of date palm trees in the MENA and the Mediterranean region, can catalyze the development of biomass and biofuels sector in the region.

Biogas from Slaughterhouse Wastes

slaughterhouse-wasteSlaughterhouse waste (or abattoir waste) disposal has been a major environmental challenge in all parts of the world. The chemical properties of slaughterhouse wastes are similar to that of municipal sewage, however the former is highly concentrated wastewater with 45% soluble and 55% suspended organic composition. Blood has a very high COD of around 375,000 mg/L and is one of the major dissolved pollutants in slaughterhouse wastewater.

In most of the developing countries, there is no organized strategy for disposal of solid as well as liquid wastes generated in abattoirs. The solid slaughterhouse waste is collected and dumped in landfills or open areas while the liquid waste is sent to municipal sewerage system or water bodies, thus endangering public health as well as terrestrial and aquatic life. Wastewater from slaughterhouses is known to cause an increase in the BOD, COD, total solids, pH, temperature and turbidity, and may even cause deoxygenation of water bodies.

Anaerobic Digestion of Slaughterhouse Wastes

There are several methods for beneficial use of slaughterhouse wastes including biogas generation, fertilizer production and utilization as animal feed. Anaerobic digestion is one of the best options for slaughterhouse waste management which will lead to production of energy-rich biogas, reduction in GHGs emissions and effective pollution control in abattoirs. Anaerobic digestion can achieve a high degree of COD and BOD removal from slaughterhouse effluent at a significantly lower cost than comparable aerobic systems. The biogas potential of slaughterhouse waste is higher than animal manure, and reported to be in the range of 120-160 m3 biogas per ton of wastes. However the C:N ratio of slaughterhouse waste is quite low (4:1) which demands its co-digestion with high C:N substrates like animal manure, food waste, crop residues, poultry litter etc.

Slaughterhouse effluent has high COD, high BOD, and high moisture content which make it well-suited to anaerobic digestion process. Slaughterhouse wastewater also contains high concentrations of suspended organic solids including pieces of fat, grease, hair, feathers, manure, grit, and undigested feed which will contribute the slowly biodegradable of organic matter. Amongst anaerobic treatment processes, the up-flow anaerobic sludge blanket (UASB) process is widely used in developing countries for biogas production from abattoir wastes.

Slaughterhouse waste is a protein-rich substrate and may result in sulfide formation during anaerobic degradation. The increased concentration of sulfides in the digester can lead to higher concentrations of hydrogen sulfide in the biogas which may inhibit methanogens. In addition to sulfides, ammonia is also formed during the anaerobic digestion process which may increase the pH in the digester (>8.0) which can be growth limiting for some VFA-consuming methanogens.