Moving Grate Incineration: Preferred WTE Technology

Incineration is the most popular waste treatment method that transforms waste materials into useful energy. The incineration process converts waste into ash, flue gas, and heat. The type of thermal WTE technology most commonly used worldwide for municipal solid waste is the moving grate incineration. These moving grate incinerators are even sometimes referred to as as the Municipal Solid Waste Incinerators (MSWIs). As of August 2013, of more than 1000 of 1200 Waste-to-Energy plants (among 40 different countries) there is no pre-treatment of the MSW before it is combusted using a moving grate. The hot combustion gases are commonly used in boilers to create steam that can be utilized for electricity production. The excess energy that can’t be used for electricity can possibly be used for industrial purposes, such as desalination or district heating/cooling

Benefits of Moving Grate

The moving grate incineration technology is lenient in that it doesn’t need prior MSW sorting or shredding and can accommodate large quantities and variations of MSW composition and calorific value. With over 100 years of operation experience, the moving grate incineration system has a long track record of operation for mixed MSW treatment. Between 2003 and 2011, it was reported that at least 106 moving grate incineration plants were built worldwide for MSW treatment. Currently, it is the main thermal treatment used for mixed MSW.

Compared to other thermal treatment technologies, the unit capacity and plant capacity of the moving grate incineration system is the highest, ranging from 10 to 920 tpd and 20 to 4,300 tpd. This system is able to operate 8,000 hours per year with one scheduled stop for inspection and maintenance of a duration of roughly one month. Today, the moving grate incineration system is the only treatment type which has been proven to be capable of treating over 3,000 tpd of mixed MSW without requiring any pretreatment steps. Being composed of six lines of furnace, one of the world’s largest moving grate incineration plants has a capacity of 4,300 tpd and was installed in Singapore by Mitsubishi in 2000

Working Principle

Moving-grate incineration requires that the grate be able to move the waste from the combustion chamber to allow for an effective and complete combustion. A single incineration plant is able to process thirty-five metric tons of waste per hour of treatment.

The MSW for a moving grate incinerator does not require pretreatment. For this reason, it is easier to process large variations and quantities. Most of these incineration plants have hydraulic feeders to feed as-received MSW to the combustion chamber (a moving grate that burns the material), a boiler to recover heat, an air pollution control system to clean toxins in the flus gas, and discharge units for the fly ash. The air or water-cooled moving grate is the central piece of the process and is made of special alloys that resist the high temperature and avoid erosion and corrosion.

Working principle of a grate incinerator

The waste is first dried on the grate and then burnt at a high temperature (850 to 950 degrees C) accompanied with a supply of air. With a crane, the waste itself is emptied into an opening in the grate. The waste then moves towards the ash pit and it is then treated with water, cleaning the ash out. Air then flows through the waste, cooling the grate. Sometimes grates can also be cooled with water instead. Air gets blown through the boiler once more (but faster this time) to complete the burning of the flue gases to improve the mixing and excess of oxygen.

Suitability for Developing Nations

For lower income and developing countries with overflowing landfills, the moving grate incinerator seems suitable and efficient. Moving grate incineration is the most efficient technology for a large-scale mixed MSW treatment because it is the only thermal technology that has been able to treat over 3,000 tons of mixed MSW per day. It also seems to be considerably cheaper than conventional technologies.

Compared to other types of Waste-to-Energy technologies, this type of system also shows the highest ability to handle variation of MSW characteristics. As for the other incineration technologies like gasification and pyrolysis technologies, these are either limited in small-scale, limited in material for industrial/hazardous waste treatment, requiring preprocessing of mixed MSW before feeding, which make them not suitable for large-scale mixed MSW treatment.

Conclusion

For the reduction of significant waste volume, treatment using a moving grate incinerator with energy recovery is the most commonly used form of waste-to-energy (WTE) technology. The moving grate’s ability to treat significant volumes of waste efficiently, while not requiring pre-treatment or sorting is a major advantage that makes this suitable for developing countries. This technology could provide many other benefits to such nations. Implementing moving grate incinerators is most suitable for developing nations because not only will it reduce waste volume, but it would also reduce the demand for landfills, and could recover energy for electricity.

References

 “A Rapidly Emerging WTE Technology: Circulating Fluid Bed Combustion”. Huang, Qunxing, Yong Chi1, and Nickolas J. Themelis. Proceedings of International Thermal Treatment Technologies (IT3), San Antonio, TX, October 2013. Columbia University. Available: http://www.seas.columbia.edu/earth/wtert/sofos/Rapid_Emerging_Tech_CFB.pdf accessed on 29 March 2016.
“Incineration.” Waste Management Resources. Waste Management Resources. Available: http://www.wrfound.org.uk/articles/incineration.html accessed on 29 March 2016.
Kamuk, Bettina, and Jørgen Haukohl. ISWA Guidelines: Waste to Energy in Low and Middle Income Countries. Rep. International Solid Waste Association, 2013. Print.
“Municipal Solid Waste Management and Waste-to-Energy in the United States, China and Japan.” Themelis, Nickolas J., and Charles Mussche. 2nd International Academic Symposium on Enhanced Landfill Mining, Houthalen and Helchteren, Belgium, 4-16 October 2013.  Enhanced Landfill Mining. Columbia University.
“Review of MSW Thermal Treatment Tecnologies.” Lai, K.C.K., I.M.C. Lo, and T.T.Z. Liu. Proceedings of the International Conference on Solid Waste 2011- Moving Towards Sustainable Resource Management, Hong Kong SAR, P.R. China, 2 – 6 May 2011. Hong Kong SAR, P.R. China. 2011. 317-321. Available: http://www.iswa.org/uploads/tx_iswaknowledgebase/10_Thermal_Technology.pdf. accessed on 14 April 2016.
UN-HABITAT, 2010. Collection of Municipal Solid Waste in Developing Countries. United Nations Human Settlements Programme (UN-HABITAT), Nairobi. Available:
http://www.eawag.ch/fileadmin/Domain1/Abteilungen/sandec/E-Learning/Moocs/Solid_Waste/W1/Collection_MSW_2010.pdf.
World Bank, 2012. What a Waste: A Global Review of Solid Waste Management. Urban Development Series Knowledge Papers. Available: http://documents.worldbank.org/curated/en/2012/03/16537275/waste-global-review-solid-wastemanagement. accessed on 14 April 2016.

Solid Waste Management in Nigeria

waste-nigeriaSolid waste management is the most pressing environmental challenge faced by urban and rural areas of Nigeria. Nigeria, with population exceeding 170 million, is one of the largest producers of solid waste in Africa. Despite a host of policies and regulations, solid waste management in the country is assuming alarming proportions with each passing day.

Nigeria generates more than 32 million tons of solid waste annually, out of which only 20-30% is collected. Reckless disposal of MSW has led to blockage of sewers and drainage networks, and choking of water bodies. Most of the wastes is generated by households and in some cases, by local industries, artisans and traders which litters the immediate surroundings. Improper collection and disposal of municipal wastes is leading to an environmental catastrophe as the country currently lack adequate budgetary provisions for the implementation of integrated waste management programmes across the States.

According to the United Nations Habitat Watch, African city populations will more than triple over the next 40 years. African cities are already inundated with slums; a phenomenon that could triple urban populations and spell disaster, unless urgent actions are initiated. Out of the 36 states and a federal capital in the country, only a few have shown a considerable level of resolve to take proactive steps in fighting this scourge, while the rest have merely paid lip services to issues of waste management indicating a huge lack of interest to develop the waste sector.

Scenario in Lagos

Lagos State, the commercial hub of Nigeria, is the second fastest growing city in Africa and seventh in the world.  The latest reports estimate its population to be more than 21 million making it the largest city in entire Africa.  With per capita waste generation of 0.5 kg per day, the city generates more than 10,000 tons of urban waste every day.

Despite being a model for other states in the country, municipal waste management is a big challenge for the Lagos State Waste Management Agency (LAWMA) to manage alone, hence the need to engage the services of private waste firms and other franchisee to reduce the burden of waste collection and disposal. One fundamental issue is the delayed collection of household solid waste.  In some cases, the wastes are not collected until after a week or two, consequently, the waste bin overflows and litters the surroundings.

Improper waste disposal and lack of reliable transport infrastructure means that collected wastes are soon dispersed to other localities. Another unwelcome practice is to overload collection trucks with 5-6 tons of waste to reduce the number of trips; this has necessitated calls by environmental activist to prevail on the relevant legislature to conform to the modern waste transportation standard.

Situation in Oyo

Away from Lagos State, Oyo is another ancient town in Nigeria with an estimated population of six million people. Here, solid waste is regulated by the Oyo State Solid Waste Management Authority (OYOWMA). Unlike Lagos State, Oyo State does not have a proper waste management scheme that cuts across the nooks and crannies of the state, apart from Ibadan, the capital city, people from other towns like Ogbomoso and Iseyin resort to waste burning. In case the waste generators feels that the amount being charged by the waste franchisee is beyond their means, they dump the waste along flood paths thus compounding the waste predicament.

Burning of municipal wastes is a common practice in Nigeria

Burning of municipal wastes is a common practice in Nigeria

Kano and Rivers State with its fair share of population also suffers similar fate in controlling and managing solid waste. Generally speaking, population increase in Nigeria has led to an unprecedented growth in its economy but with a devastating effect on the environment as more wastes are generated due to the need for housing, manufacturing industries and a boost in trade volume.

Future Perspectives

The government at the federal level as a matter of urgency needs to revive its regulatory framework that will be attractive for private sectors to invest in waste collection, recycling and reusing.  The environmental health officer’s registration council of Nigeria would do well to intensify more effort to monitor and enforce sanitation laws as well as regulate the activities of the franchisees on good sustainable practices.

Taking the advocacy further on waste management, to avoid littering the environment, some manufacturing companies (e.g. chemical and paint industry) have introduced a recall process that will reward individuals who returns empty/used plastic containers. This cash incentive has been proven over time to validate the waste to wealth program embarked upon by the manufacturing companies. It is also expected that the government will build more composting and recycling plants in addition to the ones in Ekiti and Kano State to ensure good sustainable waste management.

Waste management situation in Nigeria currently requires concerted effort to sensitize the general public on the need for proper disposal of solid waste. Also, the officials should be well trained on professionalism, service delivery and ensure that other states within the country have access to quality waste managers who are within reach and can assist on the best approach to managing their waste before collection.

Importance of Waste-to-Energy

Waste-to-energy has been evolving over the years and there are many new developments in this technology, moving in mainly one direction – to be able to applied to smaller size waste streams. Not only is it a strategy that has real importance for the current public policy, it is a strategy that will definitely present itself to additional areas.

More than 50% of waste that is burnt in waste-to-energy facilities is already part of the short carbon cycle. In which case, it has an organic derivative and it doesn’t add to climate change, to begin with. The long form carbon that is burned, things like plastics that have come out of the ground in the form of oil do add to climate change. But, they have already been used once. They have already been extracted once and what we are doing is taking the energy out of them after that physical use, capturing some of that (energy), thereby offsetting more carbon from natural gas or oil or coal. So, the net effect is a reduction in carbon emissions.

Waste-to-energy and recycling are complementary depending on the results of analyses of the First and Second Laws of Thermodynamics, which are absolutely valid. One can decide in specific situations whether waste-to-energy or whether some type of recycling technology would be more appropriate. It is not an either/or option.

In Austria, it was possible to have an absolute ban on landfilling wastes exceeding 5% organic carbon. This is written in law since 1996. There were some exceptions for some period of time, but landfills of organic wastes are just banned, not just in Austria but also in other cultures similar to Austria – like Switzerland and Germany.

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

Municipal Solid Wastes in Bahrain

The Kingdom of Bahrain is an archipelago of around 33 islands, the largest being the Bahrain Island. The population of Bahrain is around 1.2 million marked by population density of 900 persons per km2, which is the highest in the entire GCC region. The country has the distinction of being one of the highest per capita municipal solid waste generators worldwide estimated to be 1.67 – 1.80 kg per person per day. Infact, Bahrain produces largest amount of waste per person among GCC countries despite being the smallest nation in the region. Rising population, high waste generation growth rate, limited land availability and scarcity of waste disposal sites has made solid waste management a highly challenging task for Bahrain’s policy-makers, urban planners and municipalities.

Municipal Solid Wastes in Bahrain

Bahrain generates more than 1.2 million tons of solid wastes every year. Daily garbage production across the tiny Gulf nation exceeds 4,500 tons. Municipal solid waste is characterized by high percentage of organic material (around 60 percent) which is mainly composed of food wastes. Presence of high percent of recyclables in the form of paper (13 percent), plastics (7 percent) and glass (4 percent) makes Bahrain’s MSW a good recycling feedstock, though informal sectors are currently responsible for collection of collection of recyclables and recycling activities

The Kingdom of Bahrain is divided into five governorates namely Manama, Muharraq, Middle, Southern and Northern. Waste collection and disposal operation in Bahrain is managed by a couple of private contractors. Gulf City Cleaning Company is active in Muharraq and Manama while Sphinx Services is responsible for Southern, Middle, and Northern Areas. The prevalent solid waste management scenario is to collect solid waste and dump it at the municipal landfill site at Askar.

Askar, the only existing landfill/dumpsite in Bahrain, caters to municipal wastes, agricultural wastes and non-hazardous industrial wastes. Spread over an area of more than 700 acres, the landfill is expected to reach its capacity within the next few years. The proximity of Askar landfill to urban habitats has been a cause of major environmental concern. Waste accumulation is increasing at a rapid pace which is bound to have serious impacts on air, soil and groundwater quality in the surrounding areas.

Conclusions

The Kingdom of Bahrain is grappling with waste management problems arising out of high population growth rate, rapid industrialization, high per capita waste generation, unorganized SWM sector, limited land resources and poor public awareness. The government is trying hard to improve waste management scenario by launching recycling initiatives, waste-to-energy project and public awareness campaign. However more efforts, in the form of effective legislation, large-scale investments, modern SWM technology deployment and environmental awareness, are required from all stake holders to implement a sustainable waste management system in Bahrain.

Food Waste Management – Consumer Behavior and FWDs

food-waste-managementFood waste is a global issue that begins at home and as such, it is an ideal contender for testing out new approaches to behaviour change. The behavioural drivers that lead to food being wasted are complex and often inter-related, but predominantly centre around purchasing habits, and the way in which we store, cook, eat and celebrate food.

Consumer Behavior – A Top Priority

Consumer behaviour is a huge priority area in particular for industrialised nations – it is estimated that some western societies might be throwing away up to a third of all food purchased. The rise of cheap food and convenience culture in recent years has compounded this problem, with few incentives or disincentives in place at producer, retail or consumer level to address this.

While it is likely that a number of structural levers – such as price, regulation, enabling measures and public benefits – will need to be pulled together in a coherent way to drive progress on this agenda, at a deeper level there is a pressing argument to explore the psycho-social perspectives of behaviour change.

Individual or collective behaviours often exist within a broader cultural context of values and attitudes that are hard to measure and influence. Simple one-off actions such as freezing leftovers or buying less during a weekly food shop do not necessarily translate into daily behaviour patterns. For such motivations to have staying power, they must become instinctive acts, aligned with an immediate sense of purpose. The need to consider more broadly our behaviours and how they are implicated in such issues must not stop at individual consumers, but extend to governments, businesses and NGOs if effective strategies are to be drawn up.

Emergence of Food Waste Disposers

Food waste disposer (FWDs), devices invented and adopted as a tool of convenience may now represent a unique new front in the fight against climate change. These devices, commonplace in North America, Australia and New Zealand work by shredding household or commercial food waste into small pieces that pass through a municipal sewer system without difficulty.

The shredded food particles are then conveyed by existing wastewater infrastructure to wastewater treatment plants where they can contribute to the generation of biogas via anaerobic digestion. This displaces the need for generation of the same amount of biogas using traditional fossil fuels, thereby averting a net addition of greenhouse gases (GHG) to the atmosphere.

Food waste is an ideal contender for testing new approaches to behaviour change.

The use of anaerobic digesters is more common in the treatment of sewage sludge, as implemented in the U.K., but not as much in the treatment of food waste. In addition to this, food waste can also replace methanol (produced from fossil fuels) and citric acid used in advanced wastewater treatment processes which are generally carbon limited.

Despite an ample number of studies pointing to the evidence of positive impacts of FWDs, concerns regarding its use still exist, notably in Europe. Scotland for example has passed legislation that bans use of FWDs, stating instead that customers must segregate their waste and make it available curbside for pickup. This makes it especially difficult for the hospitality industry, to which the use of disposer is well suited. The U.S. however has seen larger scale adoption of the technology due to the big sales push it received in the 1950s and 60s. In addition to being just kitchen convenience appliances, FWDs are yet to be widely accepted as a tool for positive environmental impact.

Note: 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

Management of Construction Wastes

constuction-wastesA wide variety of wastes are generated during construction projects which may be classified into four categories – excavated wastes, demolition wastes, construction wastes and mixed wastes. Construction wastes are also known Construction and Demolition (C&D) wastes. Excavated materials is made up of soil, sand, gravel, rock, asphalt, etc. while demolition wastes is comprised by  concrete, metal, roofing sheets, asbestos, brick, briquette, stone gypsum, wood material. Waste materials generated from construction activities are concrete, dry wall, plastics, ceramics tiles, metals, paper, cardboards, plastics, glass etc. In addition, mixed wastes, such as trash and organic wastes, are also produced in construction projects.

Almost 90 percent of construction wastes are inert or non-hazardous, and can be reused, reclaimed and recycled and reused. The non-recyclable, non-hazardous and hazardous waste materials constitute the remaining 10 percent. The non-inert materials include trees, green vegetation, trash and other organic materials while and the hazardous construction waste materials include contaminated soil, left over paints, solvent, aerosol cans, asbestos, paint thinners, striping paint, contaminated empty containers.

Sustainable management of construction wastes uses number of strategies and is based on the typical waste hierarchy: Avoid/ eliminate, reduce, reuse, recycle, treat and dispose.

Avoidance / Source Reduction

Avoidance or source reduction is considered as the best strategy for waste management and is the most economic way to reduce waste and minimise the environmental impacts of construction wastes. This can be done by avoiding use of hazardous materials such as asbestos-containing materials or chromated copper arsenate treated timber or through green purchasing of materials. This includes purchasing of non-toxic materials, pre-cut timbers and ordering materials of desired dimensions.

Reuse

Although source reduction and elimination are preferred options in the waste management hierarchy, it is always not possible to do so. In this case consider reuse, donation and salvage options to companies or people who need those. Reuse option lengthens the life of a material. Reuse strategy can be used in two ways.

Building Reuse – It includes reusing materials from existing buildings and maintaining certain percentages of building structural and non-structural elements  such as interior walls, doors floor covering and ceilings.

Material Reuse – This is one of the most effective strategies for minimising environmental impacts which can be done by salvaging, refurbishing and reusing materials within the same building or in another building. Many of the exterior and interior materials can be recovered from existing buildings and reused in new ones. Such materials will include steel, walls, floor coverings, concrete, beams and posts, door frames, cabinetry and furniture, brick, and decorative items. Reuse of materials and products will help to reduce the demand for virgin materials and reduce wastes.

Recycle

There is very good potential to recycle many elements of construction waste. Recycling involves collecting, reprocessing and/ or recovering certain waste materials to make new materials or products. Often roll-off containers are used to transport the waste. Rubble can be crushed and reused in construction projects. Waste wood can also be recovered and recycled. Many construction waste materials that are still usable can be donated to non-profit organizations. This keeps the material out of the landfill and supports a good cause.

Treat and Dispose

This option should be considered after all other options are exhausted. The disposal of construction materials should be carried out in appropriate manner through an approved contractor. For examples, certain components of construction waste such as plasterboard are hazardous once landfilled. Plasterboard is broken down in landfill conditions releasing hydrogen sulfide, a toxic gas.

Plastic Wastes and its Management

Plastic seems all pervasive and unavoidable. Since the 1960s our use of plastic has increased dramatically, and subsequently, the portion of our garbage that is made up of plastic has also increased from 1% of the total municipal solid waste stream (household garbage) to approximately 13% (US Environmental Protection Agency). Plastic products range from things like containers and packaging (soft drink bottles, lids, shampoo bottles) to durable goods (think appliances, furniture and cars) and non-durable goods including things from a plastic party tray to medical devices. Sometimes marked with a number and a chasing arrow, there is an illusion that all plastics are recyclable, and therefore recycled. But there are a number of problems with this assumption.

While use and consumption of plastic is increasingly high, doubts about viable options for reuse, recycling and disposal are also on the rise. Complications such as the increasing number of additives used alter the strength, texture, flexibility, colour, resistance to microbes, and other characteristics of plastics, make plastics less recyclable. Additionally, there is very little market value in some plastics, leading municipalities to landfill or incinerate plastics as waste. Based on figures from the EPA (2011 data) only 8% of plastic materials are recovered through recycling.

Another major concern about plastics in the waste stream is their longevity and whether or not they are truly biodegrade. It is estimated that most plastics would take 500-1000 years to break down into organic components. Because of this longevity and the low rate of recycling, much of our plastic waste ends up in landfills or as litter. Some of this plastic waste makes its way via rivers and wind to the ocean. Garbage barges, and the trans-continental transport of recyclable materials also lead to an increasing amount of plastics in our oceans and waterways.

Plastic waste directly and indirectly affects living organisms throughout the ecosystem, including an increasingly high impact on marine life at a macro and micro scale. According to United Nations, almost 80% of marine debris is plastic. Policy enforcement remains weak, global manufacture of plastics continues to increase, and the quantity of plastic debris in the oceans, as well as on land, is likely to increase.

With limited sustainable recovery of plastics, there is a growing global movement to reduce the generation of plastic. Certain types of plastic may be ’safer‘ for the environment than others, however, there are troubling issues associated with all of them, leading to the conclusion that action is needed to remove plastic waste, and stricter controls are required to limit new sources of plastic pollution. Efforts such as light weighting of packaging and shifts to compostable plastics are options. Policies limiting the use of plastics such as bottle bills and bag bans are other ways to decrease the production and consumption of plastics.

Mining the debris fields in our oceans and turning plastic waste into usable materials, from socks made of fishing line to fuel made from a variety of plastic debris, is one way to mitigate the current situation.

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

Solid Waste Management – India’s Burning Issue

For the first time in the history of India, the year 2012 saw several public protests against improper solid waste management all across India – from the northernmost state Jammu and Kashmir to the southernmost Tamil Nadu. A fight for the right to clean environment and environmental justice led the people to large scale demonstrations, including an indefinite hunger strike and blocking roads leading to local waste handling facilities. Improper waste management has also caused a Dengue Fever outbreak and threatens other epidemics. In recent years, waste management has been the only other unifying factor leading to public demonstrations all across India, after corruption and fuel prices. Public agitation resulted in some judicial action and the government’s remedial response, but the waste management problems are still unsolved and might lead to a crisis if this continues for too long without any long term planning and policy reforms.

Hunger Strike in Kerala

The President of Vilappilsala Village Panchayat went on a hunger strike recently, against her counterpart, the Mayor of Thiruvananthapuram. Thiruvananthapuram is the state capital of Kerala, and Vilappilsala is a village 22 km away. Since July 2000, about 80% of the waste generated in Thiruvananthapuram is being transported to a waste composting plant and a dumpsite in Vilappilsala village. Since the same month, respiratory illnesses reported in Vilappil Primary Health Center increased by 10 times from an average of 450 to 5,000 cases per month. People who used to regularly swim in the village’s aquifer started contracting infections; swarms of flies have ever since been pervasive; and a stigma of filth affected households throughout the community. This was a source of frustration as locals who, as Indians, prize the opportunity to feed and host guests, found them unwilling to even drink a glass of water in their homes. Currently, there is not a single household which has not experienced respiratory illnesses due to the waste processing plant and the adjoining dumpsite.

On the other hand, Thiruvananthapuram’s residents had to sneak out at night with plastic bags full of trash to dispose them behind bushes, on streets or in water bodies, and had to openly burn heaps of trash every morning for months. This was because the waste generated was not being collected by the City as it could not force open the composting plant and dumpsite against large scale protests by Vilappilsala’s residents. This is why in August – 2012, about 2,500 police personnel had to accompany trucks to the waste treatment plant as they were being blocked by local residents lying down on the road, and by some, including the village’s President, by going on an indefinite hunger strike.

Municipal Commissioner Replaced in Karnataka

In response to a similar situation in Bengaluru, the state capital of Karnataka, where the streets were rotting with piles of garbage for months, the municipal commissioner of the city was replaced to specifically address the waste management situation. Against the will of local residents, a landfill which was closed following the orders issued by the state’s pollution control board in response to public agitation had to be reopened soon after its closure as the city could not find a new landfill site.

Mavallipura landfill in Bangalore

Population density and the scale of increasing urban sprawl in India make finding new landfill sites around cities nearly impossible due to the sheer lack of space for Locally Unwanted Land Uses (LULUs) like waste management.

Dengue Outbreak in West Bengal

Even if partially because of improper waste management, Kolkata, state capital of West Bengal and the third biggest city in India experienced a Dengue Fever outbreak with 550 confirmed cases and 60 deaths. This outbreak coincides with a 600% increase in dengue cases in India and 71% increase in malarial cases in Mumbai in the last five years. Accumulation of rain water in non biodegradable waste littered around a city act as a major breeding environment for mosquitoes, thus increasing the density of mosquito population and making the transmission of mosquito related diseases like dengue, yellow fever and malaria easier.

Rabies in Srinagar

Rabies due to stray dog bites already kills more than 20,000 people in India every year. Improper waste management has caused a 1:13 stray dog to human ratio in Srinagar (compared to 1 per 31 people in Mumbai and 1 per 100 in Chennai), where 54,000 people were bitten by stray dogs in a span of 3.5 years. Municipal waste on streets and at the dumpsite is an important source of food for stray dogs. The ultimate solution to controlling stray dogs is proper waste management. The public has been protesting about this stray dog menace for months now with no waste management solutions in sight, but only partial short term measures like dog sterilization.

Energy Potential of Coconut Biomass

coconut-shell-biomassCoconuts are produced in 92 countries worldwide on about more than 10 million hectares. Indonesia, Philippines and India account for almost 75% of world coconut production with Indonesia being the world’s largest coconut producer. A coconut plantation is analogous to energy crop plantations, however coconut plantations are a source of wide variety of products, in addition to energy. The current world production of coconuts has the potential to produce electricity, heat, fiberboards, organic fertilizer, animal feeds, fuel additives for cleaner emissions, health drinks, etc.

The coconut fruit yields 40 % coconut husks containing 30 % fiber, with dust making up the rest. The chemical composition of coconut husks consists of cellulose, lignin, pyroligneous acid, gas, charcoal, tar, tannin, and potassium. Coconut dust has high lignin and cellulose content. The materials contained in the casing of coco dusts and coconut fibers are resistant to bacteria and fungi.

Coconut husk and shells are an attractive biomass fuel and are also a good source of charcoal. The major advantage of using coconut biomass as a fuel is that coconut is a permanent crop and available round the year so there is constant whole year supply. Activated carbon manufactured from coconut shell is considered extremely effective for the removal of impurities in wastewater treatment processes.

Coconut Shell

Coconut shell is an agricultural waste and is available in plentiful quantities throughout tropical countries worldwide. In many countries, coconut shell is subjected to open burning which contributes significantly to CO2 and methane emissions.  Coconut shell is widely used for making charcoal. The traditional pit method of production has a charcoal yield of 25–30% of the dry weight of shells used. The charcoal produced by this method is of variable quality, and often contaminated with extraneous matter and soil. The smoke evolved from pit method is not only a nuisance but also a health hazard.

The coconut shell has a high calorific value of 20.8MJ/kg and can be used to produce steam, energy-rich gases, bio-oil, biochar etc. It is to be noted that coconut shell and coconut husk are solid fuels and have the peculiarities and problems inherent in this kind of fuel.  Coconut shell is more suitable for pyrolysis process as it contain lower ash content, high volatile matter content and available at a cheap cost. The higher fixed carbon content leads to the production to a high-quality solid residue which can be used as activated carbon in wastewater treatment. Coconut shell can be easily collected in places where coconut meat is traditionally used in food processing.

Coconut Husk

Coconut husk has high amount of lignin and cellulose, and that is why it has a high calorific value of 18.62MJ/kg. The chemical composition of coconut husks consists of cellulose, lignin, pyroligneous acid, gas, charcoal, tar, tannin, and potassium. The predominant use of coconut husks is in direct combustion in order to make charcoal, otherwise husks are simply thrown away. Coconut husk can be transformed into a value-added fuel source which can replace wood and other traditional fuel sources. In terms of the availability and costs of coconut husks, they have good potential for use in power plants.

Pet Waste Management in UK – Prospects and Challenges

pet-wastesPet waste is a growing public health and environmental risk. According to a report commissioned by the Pet Food Manufacturers’ Association, 13 million UK households (45%) keep pets of some kind.  Cats and dogs are each kept by 8.5 million households (these numbers are not additive, as some will of course keep both).

Can those of us who want both the joys of animal companionship and waste minimisation, find ways to cut down, or better manage, the huge amount of pet waste generated in the UK every year? With so many cats and dogs in the UK, pet waste must represent a significant mass of organic matter within the residual waste stream.

Does this waste represent a floater in the residual waste stream by necessity—due to inherently unpleasant and possibly dangerous characteristics of the waste—or is it only there out of convention and squeamishness?

I’ve written before about the relationship between waste management and squeamishness, and talking about faeces really brings the point home. There are some undoubtedly nasty pathogens present in pet faeces, notably the parasites Toxocariasis and Toxoplasmosis. But might these be safely killed off by the temperatures reached in anaerobic digestion (AD). If so, provided any litter and bags were made of organic matter, might pet waste be collected along with food waste?

I began by contacting a local authority waste officer, but was told that no one had asked this question before, and that I might be better off talking to AD plant operators. This I did, but most seemed similarly baffled by my query.  However, one mentioned that AD digestate goes through a pasteurisation process, where it is heated to a temperature of 70oC for one hour, in order to make it safe for land application. I also attempted to contact some technical specialists in the field, but to no avail.

There are some theoretical indications that this pasteurisation should be sufficient. Hanna Mizgajska-Wiktor and Shoji Uga’s  essay Exposure and Environmental Contamination states: “Anaerobic waste treatment kills Toxocara spp. eggs at temperatures in excess of 45oC”, well below the 70oC mentioned by my operator. The susceptibility of Toxoplasma to heat is less clear, although numerous internet sources suggest this can be killed in meat by cooking at 66oC. So far, then, I haven’t confirmed or falsified my initial inkling, and so the collection of pet waste in the municipal organic stream remains a theoretical possibility.

Motivated dog owners  can already turn their pet’s waste into a resource within their own home. The website London Worms explains how you can turn your dog’s poo into rich and useful vermicompost, although it warns that the results will only be suitable for use on non-edible plants.

Foul Pay

Household pet droppings may still be largely fated for disposal, but even when binned this waste is at least moving through proper waste management channels.  Unfortunately, not all pet poo is binned, and we have real data measuring public perceptions of the disamenity resulting from dog fouling. For most, the presence of this unwelcome waste in our streets, parks and footpaths is of much higher concern than its diversion from landfill.

A 2011 Defra-funded study on local residents’ willingness-to-pay — via an increase in council tax — for improvements across a range of environmental factors found that dog fouling was the third most important issue out of the presented range (with litter and fly-tipping taking first and second place). Surveys were conducted in inner-city, suburban and rural/semi-rural areas around London, Manchester and Coventry.

In order to move from the current level of dog fouling to the best possible scenario, it was found that inner-city residents would on average be willing to pay £8.87 per month, suburban residents £7.79 per month, and rural residents £2.72. Combining these figures with population statistics allows us to place a disamenity value on dog fouling. National statistics only allow for an urban-rural split, but based on a 2012 Defra rurality study which found that 18.9% of the population lives in rural areas, we can calculate that across England we would collectively be willing to pay £462m per year to achieve best case scenario improvements in dog fouling.

This somewhat crude calculation gives an indication of the perceived disamenity of dog fouling. Presenting the matter in terms such as these may allow economically minded policy makers a means of engaging with this important street scene issue and evaluating the costs and benefits of interventions.

Food for Thought

Let’s wash our hands of poo (with plenty of soap and warm water) and look to the other end of the pet waste problem. According to a report published by WRAP, the UK uses around 75,000 tonnes of primary packaging annually. This holds 1,263,000 tonnes of wet and dry cat and dog food, of which 9,000 uneaten tonnes are thrown away. Although this wasted food constitutes less than 1% of the total sold (if only we were as careful with food for human consumption) the estimated cost to the consumer is still £21m a year.

WRAP examined a number of designs intended to cut to down on the amounts of both pet food and packaging thrown away. A major problem with packaging design is the need to account for portion sizes, which vary from animal to animal and change depending on age and level of activity. Single serve packaging may actually lead to regular food wastage if the portion provided is too big for a particular pet; indeed, this is a problem I am experiencing with my own cat, whose appetite seems to fluctuate wildly. Re-sealable packaging that allows owners to dish out meals in accordance with the changing appetites of their pets is therefore preferable.

The material that packaging is made of is also significant: for example, relatively heavy tins are recyclable, whereas lightweight plasticised plastic foil packets are not. Pet food and its packaging can be pushed up the waste hierarchy by simply choosing a recyclable and resealable container which will allow them to adequately provide for the appetite of their pet. However, these issues are likely to be given less weight compared with health, convenience and cost in the minds of most householders. The onus has to be on manufacturers to develop packaging which is both low cost and easily recyclable.

Love pets, hate waste?

People love animals, but are rather less keen to engage with pets as an environmental issue. Leaving aside questions of whether it is sustainable for so many of us to have pets at all, there are clearly ways in which we can reduce their impact. The convenience of single serving pouches of pet food seems to win out over more recyclable and waste-avoiding alternatives, although pet owners might be willing to change their choices if presented with a better option.

While worrying about recovery options for cat poo might seem somewhat academic, it may be easier to tackle than dog fouling. It might even help to tackle the common psycho-social root of both issues. Cultural distaste perhaps lies behind the lack of information available on dealing with household pet waste, and the persistence of dog fouling as a street scene issue. Things were very different in Victorian London when “pure finders” earned a living by seeking out doggie doo to supply the tanning trade. But for us this kind of waste is a disagreeable fact of life which we deal with as simply and with as little thought as possible. But as a nation of animal lovers, it’s our responsibility to engage with the waste management issues our pets present.

Note: The article is being republished with the kind permission of our collaborative partner Isonomia. The original article can be viewed at this link