Food waste is an untapped energy source that mostly ends up rotting in landfills, thereby releasing greenhouse gases into the atmosphere. Food waste is difficult to treat or recycle since it contains high levels of sodium salt and moisture, and is mixed with other waste during collection. Major generators of food wastes include hotels, restaurants, supermarkets, residential blocks, cafeterias, airline caterers, food processing industries, etc.
In United States, food waste is the third largest waste stream after paper and yard waste. Around 13 percent of the total municipal solid waste generated in the country is contributed by food scraps. According to USEPA, more than 35 million tons of food waste are thrown away into landfills or incinerators each year, which is around 40 percent of all food consumed in the country.
As far as United Kingdom is concerned, households throw away around 4.5 million tons of food each year. These statistics are an indication of tremendous amount of food waste generated all over the world.
Food Waste Management Strategy
The proportion of food waste in municipal waste stream is gradually increasing and hence a proper food waste management strategy needs to be devised to ensure its eco-friendly and sustainable disposal. The two most common methods for food waste recycling are:
Composting: A treatment that breaks down biodegradable waste by naturally occurring micro-organisms with oxygen, in an enclosed vessel or tunnel;
Anaerobic digestion (AD): A treatment that breaks down biodegradable waste in the absence of oxygen, producing a renewable energy (biogas) that can be used to generate electricity and heat.
Currently, only about 3 percent of food waste is recycled throughout USA, mainly through composting. Composting provides an alternative to landfill disposal of food waste, however it requires large areas of land, produces volatile organic compounds and consumes energy. Consequently, there is an urgent need to explore better recycling alternatives.
Anaerobic digestion has been successfully used in several European and Asian countries to stabilize food wastes, and to provide beneficial end-products. Sweden, Austria, Denmark, Germany and England have led the way in developing new advanced biogas technologies and setting up new projects for conversion of food waste into energy.
Of the different types of organic wastes available, food waste holds the highest potential in terms of economic exploitation as it contains high amount of carbon and can be efficiently converted into biogas and organic fertilizer. Food waste can either be used as a single substrate in a biogas plant, or can be co-digested with organic wastes like cow manure, poultry litter, sewage, crop residues, abattoir wastes, etc.
Food waste is one of the single largest constituent of municipal solid waste stream. Diversion of food waste from landfills can provide significant contribution towards climate change mitigation, apart from generating revenues and creating employment opportunities. Rising energy prices and increasing environmental pollution makes it more important to harness renewable energy from food wastes.
Anaerobic digestion technology is widely available worldwide and successful projects are already in place in several European as well as Asian countries which makes it imperative on waste generators and environmental agencies in USA to strive for a sustainable food waste management system.
Shipping wastes, long a neglected topic, has started to attract worldwide attention, thanks to the mysterious and tragic disappearance of flight MH370. During the search for MH370, a succession of items floating in the sea were identified as possible wreckage, but later confirmed to be simply pieces of marine litter. Whilst it was large pieces of debris that complicated the search, marine debris of all sizes causes problems for users of marine resources. In the most polluted areas, around 300,000 items of debris can be found in each square kilometre.
Up to 80% of ocean debris originates from land based sources, including beach litter, litter transported by rivers, and discharges of untreated municipal sewage, while ocean based sources (merchant shipping, ferries, cruise liners, fishing and military vessels) account for the remainder. Whilst typically this may be only 20% of marine litter, in areas of high shipping activity such as the North Sea it rises closer to 40%.
Wastes from commercial vessels seems like an area that could be effectively tackled with regulation. However, it is difficult for individual nations or regions to take action when ships operate in international waters and the debris in our oceans is constantly on the move.
So how is it addressed through international legislation?
Law of the Seas
In fact, a good many laws are already in place. The key piece of legislation preventing ‘the disposal of garbage at sea’ is Annex V of the International Convention for the Prevention of Marine Pollution from Ships (MARPOL). Amongst the numerous other relevant laws are the London Convention and Protocol, the Basel Convention, UNCLOS, and the Convention on Biological Diversity.
Despite the profusion of legislation, the scale of the current and potential problems caused by marine debris, it is clear that implementation and enforcement is lagging behind. Why so?
As yet, not all coastal or flag states have ratified international instruments such as MARPOL Annex V. This means that ships registered with a non-ratified state under a‘flag of convenience’ may legally continue to discharge garbage in international waters. However, even if the current suite of international legislation was universally ratified, this would serve to expose the remaining gaps in the framework.
MARPOL Annex V includes specific requirements regarding the discharge of different types of waste and location of discharges. For instance, ground food waste can be discharged up to 3 nautical miles from land, but if it is not ground it may only be discharged at a distance of 12 nautical miles or more. Although the discharge of ‘all other garbage including plastics’ is prohibited, compliance relies upon good waste management practices on board vessels.
If waste streams are contaminated, this may result in plastics and other debris being discharged into the sea. The current approach may have been developed to accommodate shipping activity, but in practice it is somewhat confusing and it would perhaps make more sense to issue a blanket ban on discharges.
Another gap within MARPOL Annex V is the scope of the requirements for ‘garbage management plans’ and ‘garbage record books’. Vessels of 100 gross tonnes or more are required to have a garbage management plan, while vessels of 400 gross tonnes or more are required to have a garbage record book. Smaller vessels are not obliged to comply with the requirements.
Less than 1% of vessels in the world fishing fleet have a gross tonnage of over 100 tonnes, the majority has no obligation to implement and maintain a plan or book; with no planning or record keeping, the risk of illegal disposal is increased. Small fishing vessels may not be considered ‘commercial’ shipping vessels at all – thereby avoiding legislation – but they still contribute towards the problem of marine debris. Most notably, abandoned, lost or otherwise discarded fishing gear has a considerable impact on marine species through ‘ghost fishing’.
Port waste reception facilities
MARPOL Annex V requires the government of each ratified nation to provide facilities at ports for the reception of ship generated residues and garbage that cannot be discharged into the sea. The facilities must be adequate to meet the needs of ships using the port, without causing undue delay to ships. However, MARPOL does not prescribe any set standards or provide for certification. The term ‘adequate’ is instead defined in a qualitative (rather than quantitative) manner in Marine Environment Protection Committee (MEPC) resolution 83 (44).
Furthermore, MARPOL does not set any requirements regarding how waste delivered to port reception facilities should be managed. Only the non-mandatory MEPC resolution 83 (44) requires that facilities should allow for the ultimate disposal of ships’ wastes to take place in an environmentally appropriate way.
Cruise ships operate in every ocean worldwide, often in pristine coastal waters and sensitive marine ecosystems. Operators provide amenities to their passengers similar to those of luxury resort hotels, generating up to 14 tonnes of waste per day. Worldwide, the cruise industry has experienced a compound annual passenger growth rate of 7% since 1990, and the number of passengers carried is expected to increase from approximately 21 million in 2013 to 23.7 million in 2017.
The majority of current legislation on pollution and ship waste was developed prior to the rapid growth of the cruise market; as a consequence, there is no international legislation addressing the particular issues surrounding pollution and waste management on these vessels.
Although there is not yet data to support this, intuitively the amount of waste produced by ships would be linked to the number of people on board, rather than the vessel’s gross tonnage (which determines whether MARPOL rules apply). If the industry grows as forecasted, cruise ships may be responsible for a significant proportion of waste generated by ships, particularly if unmanned are the future.
To address this, onboard waste management systems that implement zero disposal of solid waste at sea are needed for cruise ships, together with a requirement that they only dispose of their waste at ports with reception facilities adequate to handle the type and volume of waste produced.
The indirect fee system aims to remove the disincentive for ships to dispose of waste at port rather than at sea by including the cost of waste disposal services in the port fees paid by visiting ships, irrespective of whether ships use the facilities
The Clean Shipping Index is an easy to use, transparent tool which can be used by cargo owners to evaluate the environmental performance of their sea transport providers. The information is entered on a ship-by-ship basis but is also added to a total carrier fleet score for an overall ranking. Questions on waste relate to garbage handling and crew awareness, and scores can only be obtained for measures that go beyond existing regulations.
One commercial container operator (Matson Navigation) has introduced a zero solid waste discharge policy. The ‘greentainer’ programme uses containers specifically designed for storing solid waste. Since 1994, this programme has prevented over 10,000 tonnes of garbage being disposed of at sea.
Currently, international legislation does not properly support a closed loop system for waste management onboard ships. Despite legislative progress and improvements in practice, the monitoring of waste from shipping remains problematic. ‘Policing the seas’ to verify what a ship discharges and where, and whether this follows recommended best practice, remains one of the most challenging aspects of waste management practice at sea, but critical to making the legal framework effective.
The United Nations Environment Programme neatly summarised the issue in 2005:“… marine litter is not a problem which can be solved only by means of legislation, law enforcement and technical solutions. It is a social problem which requires efforts to change behaviours, attitudes, management approaches and multi-sectoral involvement.”
The limitations of international legislation governing the case of marine litter disposed of at sea do need to be addressed; but unless legislation is accompanied by environmental education for seafarers, and improved monitoring, our attempts to tackle this source of marine litter will remain all at sea.
Note: The article has been republished with the permission of our collaborative partner Isonomia. The original version of the article can be found at this link.
Biomass is a key renewable energy resource that includes plant and animal material, such as wood from forests, material left over from agricultural and forestry processes, and organic industrial, human and animal wastes. The energy contained in biomass originally came from the sun. Through photosynthesis carbon dioxide in the air is transformed into other carbon containing molecules (e.g. sugars, starches and cellulose) in plants. The chemical energy that is stored in plants and animals (animals eat plants or other animals) or in their waste is called biomass energy or bioenergy.
A quick glance at popular biomass resources
What is Biomass
Biomass comes from a variety of sources which include:
Wood from natural forests and woodlands
Agricultural residues such as straw, stover, cane trash and green agricultural wastes
Crop residues encompasses all agricultural wastes such as bagasse, straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. Large quantities of crop residues are produced annually worldwide, and are vastly underutilised. Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy.
Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy. Harvesting and processing of coconuts produces quantities of shell and fibre that can be utilized.
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 thermochemically processed to produce electricity and heat. Agricultural residues are characterized by seasonal availability and have characteristics that differ from other solid fuels such as wood, charcoal, char briquette. The main differences are the high content of volatile matter and lower density and burning time.
There are a wide range of animal wastes that can be used as sources of biomass energy. The most common sources are animal and poultry manure. In the past this waste was recovered and sold as a fertilizer or simply spread onto agricultural land, but the introduction of tighter environmental controls on odour and water pollution means that some form of waste management is now required, which provides further incentives for waste-to-energy conversion.
The most attractive method of converting these organic waste materials to useful form is anaerobic digestion which gives biogas that can be used as a fuel for internal combustion engines, to generate electricity from small gas turbines, burnt directly for cooking, or for space and water heating.
Forestry residues are generated by operations such as thinning of plantations, clearing for logging roads, extracting stem-wood for pulp and timber, and natural attrition. Harvesting may occur as thinning in young stands, or cutting in older stands for timber or pulp that also yields tops and branches usable for biomass energy. Harvesting operations usually remove only 25 to 50 percent of the volume, leaving the residues available as biomass for energy.
Stands damaged by insects, disease or fire are additional sources of biomass. Forest residues normally have low density and fuel values that keep transport costs high, and so it is economical to reduce the biomass density in the forest itself.
Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Wood wastes generally are concentrated at the processing factories, e.g. plywood mills and sawmills. The amount of waste generated from wood processing industries varies from one type industry to another depending on the form of raw material and finished product.
Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings. Sawdust arise from cutting, sizing, re-sawing, edging, while trims and shaving are the consequence of trimming and smoothing of wood. In general, processing of 1,000 kg of wood in the furniture industries will lead to waste generation of almost half (45 %), i.e. 450 kg of wood. Similarly, when processing 1,000 kg of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kg wood.
The food industry produces a large number of residues and by-products that can be used as biomass energy sources. These waste materials are generated from all sectors of the food industry with everything from meat production to confectionery producing waste that can be utilised as an energy source.
Solid wastes include peelings and scraps from fruit and vegetables, food that does not meet quality control standards, pulp and fibre from sugar and starch extraction, filter sludges and coffee grounds. These wastes are usually disposed of in landfill dumps.
Liquid wastes are generated by washing meat, fruit and vegetables, blanching fruit and vegetables, pre-cooking meats, poultry and fish, cleaning and processing operations as well as wine making.
These waste waters contain sugars, starches and other dissolved and solid organic matter. The potential exists for these industrial wastes to be anaerobically digested to produce biogas, or fermented to produce ethanol, and several commercial examples of waste-to-energy conversion already exist.
Pulp and paper industry is considered to be one of the highly polluting industries and consumes large amount of energy and water in various unit operations. The wastewater discharged by this industry is highly heterogeneous as it contains compounds from wood or other raw materials, processed chemicals as well as compound formed during processing. Black liquor can be judiciously utilized for production of biogas using anaerobic UASB technology.
Municipal Solid Wastes and Sewage
Millions of tonnes of household waste are collected each year with the vast majority disposed of in open fields. The biomass resource in MSW comprises the putrescibles, paper and plastic and averages 80% of the total MSW collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the engineered landfill.
At the landfill sites, the gas produced, known as landfill gas or LFG, by the natural decomposition of MSW (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of MSW can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.
Sewage is a source of biomass energy that is very similar to the other animal wastes. Energy can be extracted from sewage using anaerobic digestion to produce biogas. The sewage sludge that remains can be incinerated or undergo pyrolysis to produce more biogas.
Food 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
The Kingdom of Saudi Arabia produces around 15 million tons of municipal solid waste (MSW) each year with average daily rate of 1.4 kg per person. With the current growing population (3.4% yearly rate), urbanization (1.5% yearly rate) and economic development (3.5% yearly GDP rate), the generation rate of MSW will become double (30 million tons per year) by 2033. The major ingredients of Saudi Arabian MSW are food waste (40-51 %), paper (12-28 %), cardboard (7 %), plastics (5-17 %), glass (3-5 %), wood (2-8 %), textile (2-6 %), metals (2-8 %) etc. depending on the population density and urban activities of that area.
In Saudi Arabia, MSW is collected and sent to landfills or dumpsites after partial segregation and recycling. The major portion of collected waste is ends up in landfills untreated. The landfill requirement is very high, about 28 million m3 per year. The problems of leachate, waste sludge, and methane and odor emissions are occurring in the landfills and its surrounding areas due to mostly non-sanitary or un-engineered landfills. However, in many cities the plans of new sanitary landfills are in place, or even they are being built by municipalities with capturing facilities of methane and leachate.
Recycling Prospects in Saudi Arabia
The recycling of metals and cardboard is the main waste recycling practice in Saudi Arabia, which covers 10-15% of the total waste. This recycling practice is mostly carried out by informal sector. The waste pickers or waste scavengers take the recyclables from the waste bins and containers throughout the cities. The waste recycling rate often becomes high (upto 30% of total waste) by waste scavengers in some areas of same cities. The recycling is further carried out at some landfill sites, which covers upto 40% of total waste by the involvement of formal and informal sectors.
The recycled products are glass bottles, aluminum cans, steel cans, plastic bottles, paper, cardboard, waste tire, etc. depending on the area, available facilities and involved stakeholders. It is estimated that 45 thousand TJ of energy can be saved by recycling only glass and metals from MSW stream. This estimation is based on the energy conservation concept, which means xyz amount of energy would be used to produce the same amount of recyclable material.
Waste-to-Energy Potential in Saudi Arabia
The possibilities of converting municipal wastes to renewable energy are plentiful. The choice of conversion technology depends on the type and quantity of waste (waste characterization), capital and operational cost, labor skill requirements, end-uses of products, geographical location and infrastructure. Several waste to energy technologies such as pyrolysis, anaerobic digestion (AD), trans-esterification, fermentation, gasification, incineration, etc. have been developed. Waste-to-energy provides the cost-effective and eco-friendly solutions to both energy demand and MSW disposal problems in Saudi Arabia.
As per conservative estimates, electricity potential of 3 TWh per year can be generated, if all of the KSA food waste is utilized in biogas plants. Similarly, 1 and 1.6 TWh per year electricity can be generated if all the plastics and other mixed waste (i.e. paper, cardboard, wood, textile, leather, etc.) of KSA are processed in the pyrolysis, and refuse derived fuel (RDF) technologies respectively.
Waste management issues in Saudi Arabia are not only related to water, but also to land, air and the marine resources. The sustainable integrated solid waste management (SWM) is still at the infancy level. There have been many studies in identifying the waste related environmental issues in KSA. The current SWM activities of KSA require a sustainable and integrated approach with implementation of waste segregation at source, waste recycling, WTE and value-added product (VAP) recovery. By 2032, Saudi government is aiming to generate about half of its energy requirements (about 72 GW) from renewable sources such as solar, nuclear, wind, geothermal and waste-to-energy systems.
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