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.

SWM in India – Role of Policies and Planning

Out of all the measures that are necessary in addressing India’s impending waste management crisis, the most efficient will be changes at the national policy and planning level. It is well known among the small but growing waste management sector that urban India will hit rock bottom due to improper waste management.

Solid-Wastes-Management-India

Unfortunately, they think such a crisis is required to bring about policy changes, as they generally tend to happen only after the damage has been done. This attitude is unfortunate because it indicates a lack of or failed effort from the sector to change policy, and also the level of India’s planning and preparedness.

Important Statistics

An average of 32,000 people will be added to urban India every day, continuously, until 2021. This number is a warning, considering how India’s waste management infrastructure went berserk trying to deal with just 25,000 new urban Indians during the last decade. The scale of urbanization in India and around the world is unprecedented with planetary consequences to Earth’s limited material and energy resources, and its natural balance.

Rate of increase in access to sanitation infrastructure generally lags behind the rate of urbanization by 33% around the world; however, the lack of planning and impromptu piecemeal responses to waste management issues observed in India might indicate a much wider gap. This means urban Indians will have to wait longer than an average urban citizen of our world for access to proper waste management infrastructure.

The clear trend in the outbreak of epidemic and public protests around India is that they are happening in the biggest cities in their respective regions. Kolkata, Bengaluru, Thiruvananthapuram, and Srinagar are capitals of their respective states, and Coimbatore is the second largest city in Tamil Nadu. However, long term national level plans to improve waste management in India do not exist and guidance offered to urban local bodies is meager.

Apart from the Jawaharlal Nehru National Urban Renewal Mission (JnNURM), there has been no national level effort required to address the problem. Even though JnNURM was phenomenal in stimulating the industry and local governments, it was not enough to address the scale and extent of the problem. This is because of JnNURM is not a long term financing program, sorts of which are required to tackle issues like solid waste management.

Role of Municipal Corporations

In the short term, municipal corporations have their hands tied and will not be able to deliver solutions immediately. They face the task of realizing waste management facilities inside or near cities while none of their citizens want them near their residences. Officials of Hyderabad’s municipal corporation have been conducting interviews with locals for about eight years now for a new landfill site, to no avail.

In spite of the mounting pressure, most corporations will not be able to close the dumpsites that they are currently using. This might not be the good news for which local residents could be waiting, but, it is important that bureaucrats, municipal officials and politicians be clear about it. Residents near Vellalore dump protested and blocked roads leading to the site because Coimbatore municipal officials repeatedly failed to fulfill their promises after every landfill fire incident.

Due to lack of existing alternatives, other than diverting waste fractionally by increasing informal recycling sector’s role, closing existing landfills would mean finding new sites. Finding new landfills in and around cities is nearly impossible because of the track record of dumpsite operations and maintenance in India and the Not in My Backyard (NIMBY) phenomenon.

However, the corporations can and should take measures to reduce landfill fires and open burning, and control pollution due to leachate and odor and vector nuisance. This will provide much needed relief to adjacent communities and give the corporations time to plan better. While navigating through an issue as sensitive this, it is of the utmost importance that they work closely with the community by increasing clarity and transparency.

Municipal officials at the meeting repeatedly stressed the issue of scarcity of land for waste disposal, which led to overflowing dumpsites and waste treatment facilities receiving more waste than what they were designed for. Most municipal officials are of the sense that a magic solution is right around the corner which will turn all of their city’s waste into fuel oil or gas, or into recycled products.

While such conversion is technologically possible with infinite energy and financial sources, that is not the reality. Despite their inability to properly manage wastes, the majority of municipal officials consider waste as “wealth” when approached by private partners. Therefore, a significant portion of officials expect royalty from private investments without sharing business risk.

Good News on the Horizon

While the situation across India is grim and official action has to be demanded through courts or public protests, there are a handful of local governments which are planning ahead and leading the way. The steps taken to solve New Delhi’s waste management problem is laudable. If it was not for the kind of leadership and determination showcased in Delhi, India would not have had its only operating WTE plant. This plant was built in 2011, at a time when the need for waste-to-energy plants was being felt all over India. 1300 tons of Delhi’s waste goes into this facility every day to generate electricity. The successful operation of this facility reinvigorated dormant projects across the nation.

After living with heaps of garbage for months, Thiruvananthapuram Municipal Corporation started penalizing institutions which dump their waste openly. It has also increased the subsidy on the cost of small scale biogas units to 75% and aerobic composting units to 90% to encourage decentralized waste management. The corporation is optimistic with the increase in number of applications for the subsidy from 10 in an entire year to 18 in just a few months after the announcement.

In Bengaluru, improper waste management led to the change of the city’s municipal commissioner. The new commissioner was handed over the job to particularly improve waste management in the city. As a response to the dengue outbreak in Kolkata, the state’s Chief Minister went door to door to create awareness about waste management, and also included the topic in her public speeches. For good or bad, many cities in India have started or initiated steps for banning plastics without performing life cycle analyses.

Pyrolysis of Municipal Wastes

Pyrolysis-MSWPyrolysis is rapidly developing biomass thermal conversion technology and has been garnering much attention worldwide due to its high efficiency and good eco-friendly performance characteristics. Pyrolysis technology provides an opportunity for the conversion of municipal solid wastes, agricultural residues, scrap tires, non-recyclable plastics etc into clean energy. It offers an attractive way of converting urban wastes into products which can be effectively used for the production of heat, electricity and chemicals.

Pyrolysis of Municipal Wastes

Pyrolysis process consists of both simultaneous and successive reactions when carbon-rich organic material is heated in a non-reactive atmosphere. Simply speaking, pyrolysis is the thermal degradation of organic materials in the absence of oxygen. Thermal decomposition of organic components in the waste stream starts at 350°C–550°C and goes up to 700°C–800°C in the absence of air/oxygen.

Pyrolysis of municipal wastes begins with mechanical preparation and separation of glass, metals and inert materials prior to processing the remaining waste in a pyrolysis reactor. The commonly used pyrolysis reactors are rotary kilns, rotary hearth furnaces, and fluidized bed furnaces. The process requires an external heat source to maintain the high temperature required. Pyrolysis can be performed at relatively small-scale which may help in reducing transport and handling costs.  In pyrolysis of MSW, heat transfer is a critical area as the process is endothermic and sufficient heat transfer surface has to be provided to meet process heat requirements.

The main products obtained from pyrolysis of municipal wastes are a high calorific value gas (synthesis gas or syngas), a biofuel (bio oil or pyrolysis oil) and a solid residue (char). Depending on the final temperature, MSW pyrolysis will yield mainly solid residues at low temperatures, less than 4500C, when the heating rate is quite slow, and mainly gases at high temperatures, greater than 8000C, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is a liquid fuel popularly known as bio oil.

Wide Range of Products

Bio oil is a dark brown liquid and can be upgraded to either engine fuel or through gasification processes to a syngas and then biodiesel. Pyrolysis oil may also be used as liquid fuel for diesel engines and gas turbines to generate electricity Bio oil is particularly attractive for co-firing because it can be relatively easy to handle and burn than solid fuel and is cheaper to transport and store. In addition, bio oil is also a vital source for a wide range of organic compounds and specialty chemicals.

Syngas is a mixture of energy-rich gases (combustible constituents include carbon monoxide, hydrogen, methane and a broad range of other VOCs). The net calorific value (NCV) of syngas is between 10 and 20MJ/Nm3. Syngas is cleaned to remove particulates, hydrocarbons, and soluble matter, and then combusted to generate electricity. Diesel engines, gas turbines, steam turbines and boilers can be used directly to generate electricity and heat in CHP systems using syngas and pyrolysis oil. Syngas may also be used as a basic chemical in petrochemical and refining industries.

The solid residue from MSW pyrolysis, called char, is a combination of non-combustible materials and carbon. Char is almost pure carbon and can be used in the manufacture of activated carbon filtration media (for water treatment applications) or as an agricultural soil amendment.

Bioenergy Resources in MENA Countries

The Middle East and North Africa (MENA) region offers almost 45 percent of the world’s total energy potential from all renewable sources that can generate more than three times the world’s total power demand. Apart from solar and wind, MENA also has abundant biomass energy resources which have remained unexplored to a great extent.

According to conservative estimates, the potential of biomass energy in the Euro Mediterranean region is about 400TWh per year. Around the region, pollution of the air and water from municipal, industrial and agricultural operations continues to grow.  The technological advancements in the biomass energy industry, coupled with the tremendous regional potential, promises to usher in a new era of energy as well as environmental security for the region.

The major biomass producing countries are Egypt, Yemen, Iraq, Syria and Jordan. Traditionally, biomass energy has been widely used in rural areas for domestic purposes in the MENA region, especially in Egypt, Yemen and Jordan. Since most of the region is arid or semi-arid, the biomass energy potential is mainly contributed by municipal solid wastes, agricultural residues and industrial wastes.

Municipal solid wastes represent the best source of biomass in Middle East countries. Bahrain, Saudi Arabia, UAE, Qatar and Kuwait rank in the top-ten worldwide in terms of per capita solid waste generation. The gross urban waste generation quantity from Middle East countries is estimated at more than 150 million tons annually. Food waste is the third-largest component of generated waste by weight which mostly ends up rotting in landfill and releasing greenhouse gases into the atmosphere. The mushrooming of hotels, restaurants, fast-food joints and cafeterias in the region has resulted in the generation of huge quantities of food wastes.

In Middle East countries, huge quantity of sewage sludge is produced on daily basis which presents a serious problem due to its high treatment costs and risk to environment and human health. On an average, the rate of wastewater generation is 80-200 litres per person each day and sewage output is rising by 25 percent every year. According to estimates from the Drainage and Irrigation Department of Dubai Municipality, sewage generation in the Dubai increased from 50,000 m3 per day in 1981 to 400,000 m3 per day in 2006.

The food processing industry in MENA produces a large number of organic residues and by-products that can be used as biomass energy sources. In recent decades, the fast-growing food and beverage processing industry has remarkably increased in importance in major countries of the region. Since the early 1990s, the increased agricultural output stimulated an increase in fruit and vegetable canning as well as juice, beverage, and oil processing in countries like Egypt, Syria, Lebanon and Saudi Arabia.

The MENA countries have strong animal population. The livestock sector, in particular sheep, goats and camels, plays an important role in the national economy of respective countries. Many millions of live ruminants are imported each year from around the world. In addition, the region has witnessed very rapid growth in the poultry sector. The biogas potential of animal manure can be harnessed both at small- and community-scale.

Waste-to-Energy Prospects in the Middle East

wastetoenergy-plant-qatarA combination of high fuel prices and a search for alternative technologies, combined with massive waste generation has led to countries in the Middle East region to consider Waste to Energy (or WtE) as a sustainable waste management strategy and cost-effective fuel source for the future. We look at the current state of the WtE market in the region.

It is estimated that each person in the United Arab Emirates produces 2 kg of municipal solid waste per day – that puts the total waste production figure somewhere in the region of 150 million tonnes every year. Given that the population currently stands at over 9.4 million (2013) and is projected to see an annual average growth figure of 2.3% over the next six years, over three times the global average, it’s clear that this is a lot of waste to be disposed of. In addition, the GCC nations in general rank in the bottom 10% of the sustainable nations in the world and are also amongst the top per capita carbon-releasers.

When we also consider that UAE are actively pursuing alternative energy technologies to supplement rapidly-decreasing and increasingly-costly traditional fossil fuels, mitigate the harmful effects of landfill, and reduce an ever-increasing carbon footprint, it becomes apparent that high on their list of proposed solutions is Waste to Energy (WtE). It could be an ideal solution to the problem.

What is WtE

Waste-to-Energy works on the simple principle of taking waste and turning it into a form of energy. This can be electricity, heat or transport fuels, and can be achieved in a variety of ways – the most common of which is incineration. MSW is taken to a WtE plant, incinerated at high temperatures and the resultant heat is used to boil water which creates steam to turn turbines, in the same way that burning gas or coal produces power. Gasification and anaerobic digestion are two further WtE methods which are also used.

However, WtE has several advantages over burning fossil fuels. Primarily amongst them are the potential to minimise landfill sites which have caused serious concern for many years. They are not only unsightly, but can also be contaminated, biologically or chemically. Toxic waste can leach into the ground beneath them and enter the water table.

Landfill sites also continuously emit carbon dioxide and methane, both harmful greenhouse gases – in addition methane is potentially explosive. Sending MSW to landfill also discourages recycling and necessitates more demand for raw materials. Finally, landfill sites are unpleasant places which attract vermin and flies and give off offensive odours.

WtE has been used successfully in many countries around the world for a long time now. Europe is the most enthusiastic proponent of WtE, with around 450 facilities; the Asia-Pacific region has just over 300; the USA has almost 100. In the rest of the world there are less than 30 facilities but this number is growing. Globally, it is estimated that the WtE industry is growing at approximately US $2 billion per annum and will be valued at around US $80 billion by the year 2022.

The USA ranks third in the world for the percentage of waste which is incinerated for energy production. Around 16% of the rubbish that America produces every day is burned in its WtE plants. Advocates claims the advantages are clear: reducing the amount of greenhouse gas emitted into the environment (estimates say that burning one ton of waste in a WtE plant saves between one half and one ton of greenhouse gases compared to landfill emissions, or the burning of conventional fuels), freeing up land which would normally be used for landfill (and, therefore, extending the life of existing landfill sites), encouraging recycling (some facilities have managed to reduce the amount of waste they process by up to 90% and the recycling of ferrous and non-ferrous metals provides an additional income source), and, perhaps most importantly, producing a revenue stream from the sale of the electricity generated.

In one small county alone, Lancaster, Pennsylvania, with a population of just over half-a-million people, more than 4.4 billion kWh of electricity has been produced through WtE in the last 20 years. This has generated over USD $256 million through its sale to local residents.

WtE in the Middle East

Given WtE’s potential to not only reduce greenhouse gas emissions and pollution on a local scale, but also to produce much-needed electricity in the region, what is the current state of affairs in the Middle East. There are several WtE initiatives already underway in the region. Qatar was the first GCC country to implement a waste-to-energy programme and currently generates over 30MW of electricity from its Domestic Solid Waste Management Center (DSWMC) located at Messeid (Doha). Saudi Arabia and the UAE have both stated that they have WtE production capacity targets of 100MW. Bahrain, Kuwait and Oman are also seriously considering waste-to-energy as a means to tackle the worsening waste management problem.

Abu Dhabi’s government is currently spending around US $850 million to build a 100 MW plant which is expected to be operational by 2017 and which will supply around 20,000 households with electricity. In Sharjah, the world’s largest household waste gasification plant, costing in excess of US $480 million, is due to be open in 2015.

However, not all the GCC members are as enthusiastic about WtE. Dubai’s government has recently scrapped plans for a US $2 billion project which would have made use of the 7,800 tonnes of domestic waste which is produced in Dubai every single day.

We asked Salman Zafar, Founder of Doha-based EcoMENA, a popular sustainability advocacy, why given the sheer scale of the waste in the Gulf region, the production of this form of energy is still in its infancy. “The main deterrent in the implementation of WtE projects in the Middle East is the current availability of cheap sources of energy already available, especially in the GCC,” he commented.

Salman Zafar further says, “WtE projects demand a good deal of investment, heavy government subsidies, tipping fees, power purchase agreements etc, which are hard to obtain for such projects in the region.” “The absence of a sustainable waste management strategy in Middle East nations is also a vital factor behind the very slow pace of growth of the WtE sector in the region. Regional governments, municipalities and local SWM companies find it easier and cost-effective to dump untreated municipal waste in landfills,” he added.

So, how can WtE contribute towards the region’s growing power demand in the future?

“Modern WtE technologies, such as RDF-based incineration, gasification, pyrolysis, anaerobic digestion etc, all have the ability to transform power demand as well as the waste management scenario in the region,” he continued. “A typical 250 – 300 tons per day WtE plant can produce around 3 – 4 MW of electricity and a network of such plants in cities across the region can make a real difference in the energy sector as well as augmenting energy reserves in the Middle East. In fact, WtE plants also produce a tremendous about of heat energy which can be utilised in process industries, further maximising their usefulness,” Salman Zafar concluded.

New technologies naturally take time to become established as their efficiency versus cost ratios are analysed. However, it is becoming increasingly clearer that waste-to-energy is a viable and efficient method for solid waste management and generation of alternative energy in the Middle East.

Concept of Zero Waste and Role of MRFs

zero-waste-MRFCommunities across the world are grappling with waste disposal issues. A consensus is emerging worldwide that the ultimate way to deal with waste is to eliminate it. The concept of Zero Waste encourages redesign of resource life cycles so that all products are reused, thereby systematically avoiding and eliminating the volume and toxicity of waste and materials.

The philosophy of Zero Waste strives to ensure that products are designed to be repaired, refurbished, re-manufactured and generally reused. Among key zero waste facilities are material recovery facilities, composting plants, reuse facilities, wastewater/biosolids plants etc.

Material recovery facilities (MRFs) are an essential part of a zero waste management program as it receives separates and prepares recyclable materials for marketing to end-user manufacturers. The main function of the MRF is to maximize the quantity of recyclables processed, while producing materials that will generate the highest possible revenues in the market. MRFs can also process wastes into a feedstock for biological conversion through composting and anaerobic digestion.

A materials recovery facility accepts materials, whether source separated or mixed, and separates, processes and stores them for later use as raw materials for remanufacturing and reprocessing. MRFs serve as an intermediate processing step between the collection of recyclable materials from waste generators and the sale of recyclable materials to markets for use in making new products. There are basically four components of a typical MRF: sorting, processing, storage, and load-out. Any facility design plan should accommodate all these activities which promote efficient and effective operation of a recycling program. MRFs may be publicly owned and operated, publicly owned and privately operated, or privately owned and operated.

There are two types of MRFs – dirty and clean. A dirty MRF receives mixed waste material that requires labor intense sorting activities to separate recyclables from the mixed waste. A clean MRF accepts recyclable materials that have already been separated from the components in municipal solid waste (MSW) that are not recyclable. A clean MRF reduces the potential for material contamination.

A typical Zero Waste MRF (ZWMRF) may include three-stream waste collection infrastructure, resource recovery center, reuse/recycling ecological part, residual waste management facility and education centers.

The primary objective of all MRFs is to produce clean and pure recyclable materials so as to ensure that the commodities produced are marketable and fetch the maximum price. Since waste streams vary in composition and volume from one place to another, a MRF should be designed specifically to meet the short and long term waste management goals of that location. The real challenge for any MRF is to devise a recycling strategy whereby no residual waste stream is left behind.

The basic equipment used in MRFs are conveyors & material handling equipment to move material through the system, screening equipment to sort material by size, magnetic separation to remove ferrous metals, eddy current separation to remove non-ferrous metals, air classifiers to sort materials by density, optical sorting equipment to separate plastics or glass by material composition, and baling equipment to prepare recovered material for market. Other specialized equipment such as bag breakers, shredders and sink-float tanks can also be specified as required by application.

Municipal Wastes in Saudi Arabia

Saudi Arabia has been witnessing rapid industrialization, high population growth rate and fast urbanization which have resulted in increased levels of pollution and waste. Solid waste management is becoming a big challenge for the government and local bodies with each passing day. With population of around 29 million, Saudi Arabia generates more than 15 million tons of solid waste per year. The per capita waste generation is estimated at 1.5 to 1.8 kg per person per day.

Solid waste generation in the three largest cities – Riyadh, Jeddah and Dammam – exceeds 6 million tons per annum which gives an indication of the magnitude of the problem faced by civic bodies.  More than 75 percent of the population is concentrated in urban areas which make it necessary for the government to initiate measures to improve recycling and waste management scenario in the country.

In Saudi Arabia, municipal solid waste is collected from individual or community bins and disposed of in landfills or dumpsites. Saudi waste management system is characterized by lack of waste disposal and tipping fees. Recycling, reuse and energy recovery is still at an early stage, although they are getting increased attention. Waste sorting and recycling are driven by an active informal sector. Recycling rate ranges from 10-15%, mainly due to the presence of the informal sector which extracts paper, metals and plastics from municipal waste.

Recycling activities are mostly manual and labor intensive. Composting is also gaining increased interest in Saudi Arabia due to the high organic content of MSW (around 40%).  Efforts are also underway to deploy waste-to-energy technologies in the Kingdom. All activities related to waste management are coordinated and financed by the government.

The Saudi government is aware of the critical demand for waste management solutions, and is investing heavily in solving this problem. The 2011 national budget allocated SR 29 billion for the municipal services sector, which includes water drainage and waste disposal. The Saudi government is making concerted efforts to improve recycling and waste disposal activities.

Waste Management Scenario in Oman

Waste management is a challenging issue for the Sultanate of Oman due to high waste generation rates and scarcity of disposal sites. With population of almost 3 million inhabitants, the country produced about 1.6 million tons of solid waste in 2010. The per capita waste generation is more than 1.5 kg per day, among the highest worldwide.

Solid waste in Oman is characterized by very high percentage of recyclables, primarily paper (26%), plastics (12%), metals (11%) and glass (5%). However the country is yet to realize the recycling potential of its municipal waste stream. Most of the solid waste is sent to authorized and unauthorized dumpsites for disposal which is creating environment and health issues. There are several dumpsites which are located in the midst of residential areas or close to catchment areas of private and public drinking water bodies.

Solid waste management scenario in marked by lack of collection and disposal facilities. Solid waste, industrial waste, e-wastes etc are deposited in very large number of landfills scattered across the country. Oman has around 350 landfills/dumpsites which are managed by municipalities. In addition, there are numerous unauthorized dumpsites in Oman where all sorts of wastes are recklessly dumped.

Al Amerat landfill is the first engineered sanitary landfill in Oman which began its operations in early 2011. The landfill site, spread over an area of 9.6 hectares, consists of 5 cells with a total capacity of 10 million m3 of solid waste and spread over an area of over 9.6 hectares. Each cell has 16 shafts to take care of leachate (contaminated wastewater). All the shafts are interconnected, and will help in moving leachate to the leachate pump. The project is part of the government’s initiatives to tackle solid waste in a scientific and environment-friendly manner. Being the first of its kind, Al Amerat sanitary landfill is expected to be an example for the future solid waste management projects in the country.

Solid waste management is among the top priorities of Oman government which has chalked out a robust strategy to resolve waste management problem in the Sultanate. The country is striving to establish engineered landfills, waste transfer stations, recycling projects and waste-to-energy facilities in different parts of the country.  Modern solid waste management facilities are under planning in several wilayat, especially Muscat and Salalah. The new landfills will eventually pave the way for closure of authorized and unauthorized garbage dumps around the country. However investments totaling Omani Rial 2.5 billion are required to put this waste management strategy into place.

The state-owned Oman Environment Services Holding Company (OESHCO), which is responsible for waste management projects in Oman, has recently started the tendering process for eight important projects. OESHCO has invited tenders from specialised companies for an engineered landfill and material recovery facility in Barka, apart from advisory services for 29 transfer stations and a couple of tenders for waste management services in the upcoming Special Economic Zone (SEZ) in Duqm, among others. Among the top priorities is that development of Barka engineered landfill as the existing Barka waste disposal site, which serve entire wilayat and other neighbouring wilayats in south Batinah governorate, is plagued by environmental and public health issues.

Biofuels from MSW – An Introduction

Nowadays, biofuels are in high demand for transportation, industrial heating and electricity generation. Different technologies are being tested for using MSW as feedstock for producing biofuels. This article will provide brief description of biochemical and thermochemical conversion routes for the production of biofuels from municipal solid wastes.

drop-in-biofuels

Biochemical conversion

The waste is collected and milled, particles are shredded to reduce the size of 0.2-1.22 mm. MSW is pretreated to improve the accessibility of enzymes and make use of the enzymes in the bacteria for biological degradation on solid waste. The mixture of biomass is mixed with sulfuric acid and sodium hydroxide and autoclaved. After steam treatment, the mixture is filtered and washed with deionized water. The pre-treated mixture is then dried and drained overnight. The pre-treatment process improves the formation of sugars by enzymatic hydrolysis, avoids the loss of carbohydrate and avoids the formation of by-products inhibitory.

After pre-treatment (pre-hydrolysis), the mixture undergoes enzymatic hydrolysis for conversion of polysaccharides into monomer sugars, such as glucose and xylose. The common enzymes used for starch-based substrates are ?- and ?- amylase, pullulanase, isomylase and glucoamylase. Whereas for lignocellulose based substrates cellulases and ?- glucosidases.

Finally, the mixture is fermented; sugars are converted to ethanol by using microorganisms such as, bacteria, yeast or fungi. The cellulosic and starch hydrolysates ethanolic fermentation were fermented by M. indicus at 37 °C for 72 h. The fungus uses the hexoses and pentoses sugars with a high concentration of inhibitors (i.e. furfural, hydroxymethyl furfural, and acetic acid).

The composition of MSW feedstock effects the yield of the subsequent processes. A high composition of food and vegetable waste is more desirable, as these wastes are easily degradable and result in high yields compared to paper and cardboard.

Thermochemical conversion

Gasification process is carried out by treating carbon-based material with either oxygen or steam to produce a gaseous fuel which requires high temperature and pressure. It can be described as partial oxidation of the waste. At first waste is reduced in size and dried to reduce the amount of energy used in the gasifier.

Biomass_Gasification_Process

Layout of a Typical Biomass Gasification Plant

 

The carbonaceous material oxidizes (combines with oxygen) to produce syngas (carbon monoxide and hydrogen) along with carbon dioxide, methane, water vapor, char, slag, and trace gases (depending on the composition of the feedstock). The syngas is then cleaned to remove any sulfur or acid gases and trace metals (depending on the composition of the feedstock).

The main uses of syngas are direct burning on site to provide heat or energy (by using boilers, gas turbines or steam driven engines) and refined to liquid fuels such as gasoline or ethanol.

Syngas can then be converted into biofuels and chemicals via catalytic processes such as the Fischer-Tropsch process. The Fischer-Tropsch process is a series of catalytic chemical reactions that convert syngas into liquid hydrocarbons by applying heat and pressure. Hydrocracking, hydro-treating, and hydro-isomerization can also be part of the “upgrading” process to maximize quantities of different products.

Waste-to-Energy in Saudi Arabia

waste-jeddahUrban waste management has emerged as a big challenge for the government and local bodies in Saudi Arabia. The country generates more than 15 million tons of municipal solid waste each year with per capita waste production estimated to be 2 kg per day, among the highest worldwide. Municipal waste production in three largest cities – Riyadh, Jeddah and Dammam – exceeds 6 million tons per annum which gives an indication of the enormity of the problem faced by civic bodies.

The Problem of Waste

Municipal waste generation in Saudi Arabia is increasing at an unprecedented rate. Due to high population growth rate, rapid urbanization and fast-paced economic development, MSW generation is expected to cross 30 million tons per year by 2033. More than 75 percent of Kingdom’s population is concentrated in urban areas, and collected garbage is thrown in landfills or dumpsites without any processing or treatment.

Most of the landfills in Saudi Arabia are non-sanitary and prone to problems like leachate, vermin, flies and spontaneous fires, apart from greenhouse gas emissions.  It has become necessary for the Saudi government to devise an integrated waste management strategy, using international best practices and modern technologies, to tackle heaps of garbage accumulating across the country.

Promise of Waste-to-Energy

Waste-to-energy provides a cost-effective and eco-friendly solution to both energy demand and MSW disposal problems in Saudi Arabia. Increasing waste generation, inability of existing solutions to tackle waste and expansion of cities into ex-dump sites are strong drivers for large-scale deployment of WTE systems in the Kingdom.

Saudi Arabia has tremendous waste-to-energy potential due to plentiful availability of good quality municipal waste. Modern waste-to-energy technologies, such as RDF-based incineration, gasification, pyrolysis and anaerobic digestion have the ability to transform power demand and waste management scenario in the country.

A typical 250 – 300 tons per day garbage-to-energy plant can produce around 3 – 4 MW of electricity and a network of such plants in cities around the country can make a real difference in waste management as well as energy sectors.  In fact, such plants also produce tremendous about of heat energy which can be utilized in process industries and district cooling systems, further maximizing their usefulness.

Key Challenges

Around the world, waste-to-energy finds wide acceptance as a tool to manage urban wastes, with more than 1,000 waste-to-energy plants in operation globally, especially in Europe, China and the Asia-Pacific. However, waste-to-energy is struggling to get off-the-ground in Saudi Arabia due to several issues, the main reason being the cheap and plentiful availability of oil which prevents decision-makers to set effective regulations for waste-to-energy development in the country.

Waste-to-Energy is widely accepted as a part of sustainable waste management strategy worldwide.

Waste-to-Energy is widely accepted as a part of sustainable waste management strategy worldwide.

Policy-makers in KSA should consider waste-to-energy as a sustainable waste management solution, rather than as a power-producing industry. Unlike Western countries, waste management services are practically free-of-cost for the waste generators which act as a deterrent for governmental investment in new waste management solutions and technologies, such as waste-to-energy. Infact, waste collection, transport and disposal methods in Saudi Arabia do not match the standards of a developed country.

Future Outlook

Vision 2030, touted as most comprehensive economic reform package in Saudi history, puts forward a strong regulatory and investment framework to develop Saudi waste-to-energy sector. An ambitious target of 3GW of energy from waste is to be achieved by 2025.  A methodical introduction of modern waste management techniques like material recovery facilities, waste-to-energy systems and recycling infrastructure can significantly improve waste management scenario and can also generate good business opportunities.

To sum up, environmental issues associated with non-sanitary landfills, ineffectiveness of prevalent waste management model and rising energy demand are key drivers for development of waste-to-energy sector in Saudi Arabia.