Pyrolysis is the thermal decomposition of complex organic matter in the absence of oxygen to simpler molecules that can be used as feedstocks for many processes. The main products produced by the pyrolysis process are
activated carbon,
biodiesel and
syngas.
Pyrolysis always consists of the endothermic reaction, though general combustion is done by the generation of heat reaction in the system
that produces solid, liquid, and gas, heating it at moderately high temperatures under a no oxygen or low oxygen atmosphere.
Biodiesel produced by the process of pyrolysis can be used purely as a fuel or for other petroleum products. The syngas is typically used for
combustion or to run turbines for power generation, including running the plant itself.
The biomass used in pyrolysis is typically composed of cellulose, hemicellulose, and lignin. The main parameters that govern the pyrolysis
process are
temperature,
heating rate,
solid residence time,
volatile residence time,
particle size and
density of particles.
Pyrolysis is, therefore categorised into three major types:
flash,
fast and
slow pyrolysis
and are respectively based on
temperature,
heating rate and
residence time.
The products of pyrolysis thus vary dramatically according to type. Cellulose is converted to
‘Electronic Waste’. Electronic waste covers everything from home appliances like TVs, air conditioners, and fans to IT devices like computers and mobiles that have been replaced or have reached the end of their life cycle and need to be disposed of.
Waste electrical and electronic equipment (WEEE) is becoming a major threat to the whole world. Its toxic emissions mixed with virgin soil and air and causing harmful effects to the entire biota either directly or indirectly. Direct impacts include the release of acids, toxic compounds including heavy metals, carcinogenic chemicals and indirect effects such as biomagnification of heavy metals. Many private firms are involved in collecting, dismantling, separation and exporting e-wastes for recyclers. However, strict regulations are currently being followed as on approval of such firms such as e-steward certification by Basel action network in the USA, they also involved in public awareness programs; this review is based on collected information from various journal articles, websites including the technical note by Greenpeace international. Further, it analyzes the current progress on e-waste management worldwide.
Here’s an example to understand the scale of the problem, according to estimates by Ceylon Waste Management there are 7.6 Million CRT TVs and Monitors in Sri Lanka, and only 10% of that will be properly disposed. The remaining 90% will be around 67500 metric tons of CRTs, of which 8840 tons will be lead and 110 tons of arsenic. That’s a massive amount of poison that could leach into our ecosystem endangering both human and animal lives. Other methods must be employed to dispose of this waste.
What Happens to Devices at the End of Their Useful Life
Unfortunately, the majority of these electronic products end up in landfills, and just 12.5% of e-waste is recycled. According to a UN study, over 41.8 million tons of e-waste was discarded worldwide, with only 10%–40% percent of disposals appropriately done. Electronics are full of valuable materials, including copper, tin, iron, aluminum, fossil fuels, titanium, gold, and silver. Many of the materials used in making these electronic devices can be recovered, reused, and recycled—including plastics, metals, and glass.
In a report, Apple revealed that it recovered 2,204 pounds of gold —worth $40 million—from recycled iPhones, Macs, and iPads in 2015.
Benefits of E-Waste Recycling
Recycling e-waste enables us to recover various valuable metals and other materials from electronics, saving natural resources (energy), reducing pollution, conserving landfill space, and creating jobs. According to the EPA, recycling one million laptops can save the energy equivalent of electricity that can run 3,657 U.S. households for a year. Recycling one million cell phones can also recover 75 pounds of gold, 772 pounds of silver, 35,274 pounds of copper, and 33 pounds of palladium.
On the other end, e-waste recycling helps cut down on production waste. According to the Electronics TakeBack Coalition, it takes 1.5 tons of water, 530 lbs of fossil fuel, and 40 pounds of chemicals to manufacture a single computer and monitor. 81% of the energy associated with a computer is used during production and not during operation.
The Electronics Recycling Process
Electronics recycling can be challenging because discarded electronics devices are sophisticated devices manufactured from varying proportions of glass, metals, and plastics. The process of recycling can vary, depending on the materials being recycled and the technologies employed, but here is a general overview.
Collection and Transportation: Collection and transportation are two of the initial stages of the recycling process, including for e-waste. Recyclers place collection bins or electronics take-back booths in specific locations and transport the collected e-waste from these sites to recycling plants and facilities.
Shredding, Sorting, and Separation:After collection and transportation to recycling facilities, materials in the e-waste stream must be processed and separated into clean commodities that can be used to make new products. Efficient separation of materials is the foundation of electronics recycling. Shredding the e-waste facilitates the sorting and separation of plastics from metals and internal circuitry, and waste items are shredded into pieces as small as 100mm to prepare for further sorting.
A powerful overhead magnet separates iron and steel from the waste stream on the conveyor and then prepares it for sale as recycled steel. Further mechanical processing separates aluminum, copper, and circuit boards from the material stream—which now is mostly plastic. Water separation technology is then used to separate glass from plastics. The final step in the separation process locates and extracts any remaining metal remnants from the plastics to purify the stream further.
Preparation For Sale as Recycled Materials:After the shredding, sorting and separation stages have been executed, the separated materials are prepared for sale as usable raw materials for the production of new electronics or other products.
Electronics Recycling Associations
ISRI (the Institute of Recycling Industries):ISRI is the largest recycling industry association with 1600 member companies, of which 350 companies are e-waste recyclers.
CAER (Coalition for American Electronics Recycling): CAER is another leading e-waste recycling industry association in the U.S. with over 130 member companies operating around 300 e-waste recycling facilities altogether throughout the country.
EERA (European Electronics Recyclers Association):EERA is the leading e-waste recycling industry association in Europe.
EPRA (Electronic Products Recycling Association):EPRA is the leading e-waste recycling industry association in Canada.
Current Challenges for Electronics Recycling Industry
The E-waste recycling industry has a significant number of challenges, which the primary one being exporting to developing nations. Exporting e-waste, including hazardous and toxic materials, is leading to serious health hazards for the workers working for dismantling electronic devices in countries without adequate environmental controls. Currently, 50%–80% of e-waste that recyclers collect is exported overseas, including illegally exported e-scrap, which is of particular concern. Overall, the inadequate management of electronics recycling in developing countries has led to various health and environmental problems.
Although the volume of e-waste is increasing rapidly, the quality of e-waste is decreasing. Devices are getting smaller and smaller, containing less precious metal. The material values of many end-of-life electronic and electrical devices have therefore fallen sharply. Electronics recyclers have suffered due to sagging global prices of recycled commodities, which have decreased margins and resulted in business closures.
Another problem is that as time goes on, many products are being made in ways that make them not easily recyclable, repairable, or reusable. Such design is often undertaken for proprietary reasons, to the detriment of overall environmental goals. Organizations such as ISRI have been active in promoting policies to broaden the range of authorized companies allowed to repair and refurbish smartphones to avoid their needless destruction.The current rate or level of e-waste recycling is definitely not sufficient. The current recycling rate of 15%–18% has much room for improvement as most e-waste still is relegated to the landfill.
Electronics Recycling Laws
Currently, 25 U.S. states have laws mandating statewide e-waste recycling, and several more states are working toward passing new legislation and improving the existing policy. State e-waste recycling laws cover 65% of the U.S. population, and some states, including California, Connecticut, Illinois, and Indiana, e-waste is banned from landfills.
Potential Initiatives in Sri Lanka
Despite these initiatives, Sri Lanka is still far away in terms of e-waste management compared to most countries. Thus, existing bottlenecks need to be addressed in order for Sri Lanka to be a sustainable e-waste recycler. Strengthening policy and legislation is vital. Apart from the existing policy and regulation, the government could reinforce regulations, specifically on the imports of EEE. For instance, regulations should be enacted on discouraging the imports of used EEE, and to import equipment that has less hazardous elements; for example, LED/LCD monitors can replace CRT monitors, since CRT has more hazardous elements. In addition, suitable technology and skills need to be implemented in order to streamline the sustainable e-waste recycling system in the country. Proper mechanisms should also be developed to take out the informal market for e-waste recycling in the country. Improving the knowledge on e-waste within the community is crucial. Conducting programmes which highlight the social and ecological impacts of improper handling of e-waste, and the importance of disposing e-waste in proper places and in proper ways can be effective in raising public awareness. This can be provided through the public health staff, starting from grassroots levels. Also, the media can play a pivotal role in disseminating the message and making the mass community aware of the impacts of improper handling of e-waste as well as the proper mechanisms in recycling and its benefits.
‘E-waste’ should not be considered as normal ‘junk’. It may not impact you instantaneously, but could do so later in life. Therefore, much attention should be paid to this issue, considering the many health impacts that could be instigated by the e-waste around us.
Construction activities can generate large amounts of waste
materials that then need to be disposed of. In addition, at the end of a
building's life, it may be deconstructed or demolished, generating significant
amounts of waste. Construction waste includes the waste that is generated during
construction activities (such as packaging, or the products of demolition) and
materials that are surplus to requirements (as a result of over-ordering or
inaccurate estimating).
Typical construction waste products can include:
Insulation and asbestos materials.
Concrete, bricks, tiles and ceramics.
Wood, glass and plastic.
Bituminous mixtures, coal tar and tar.
Metallic waste (including cables and pipes).
Soil, contaminated soil, stones and dredging spoil.
Gypsum.
Cement.
Paints and varnishes.
Adhesives and sealants.
Increasingly, there are options available in terms of
reusing and recycling materials, and reducing the amount of waste produced in
the first place, but despite this, a large amount of construction waste is still
disposed of in a landfill. 32% of landfill waste comes from the construction and
demolition of buildings and 13% of products delivered to construction sites are
sent directly to the landfill without having being used (ref. Technology Strategy
Board)
This can be an expensive process, as the 1996 Finance Act
introduced a tax on waste disposal on all landfill sites registered in the UK.
To help tackle this, a site waste management plan (SWMP) can
be prepared before construction begins, describing how materials will be
managed efficiently and disposed of legally during the construction of the
works, and explaining how the re-use and recycling of materials will be
maximised. For more information, see Site waste management plan.
It may be possible to eliminate a certain amount of
construction waste through careful planning. For example, steel formwork
systems might be capable of being used for concrete works which can then be
reused elsewhere on the project/s in place of timber formwork which is classed
as waste once it has been used.
Other types of construction waste may be capable of being
minimised; for example, products which are provided with reduced packaging or
those which are composed of recycled materials. There can also be opportunities
to re-use materials and products which are in a suitable condition (e.g. doors,
windows, roof tiles and so on), or exchange them for other materials with a
different construction site.
Materials and products which cannot be eliminated, minimised
or reused may have to be disposed of as waste. Before sending waste for
disposal, it should be sorted and classified to allow waste contractors to
manage it effectively and ensure that hazardous waste is properly handled.
The Problem
Disposal of public fill at public filling areas and mixed construction waste at sorting facilities or landfills has been the major approach for construction waste management. For sustainable development, we can no longer rely solely on reclamation to accept most of the inert construction waste. As such, the government is examining ways to reduce and also to promote the reuse and recycling of construction waste. Nevertheless, there will still be a substantial amount of materials that require disposal, either at public fill reception facilities or at landfills.
Today, we are running out of both reclamation sites and landfill space. With the current trend, our landfills will be full in mid to late-2010s, and public fill capacity will be depleted in the near future. In 2013, the mixed construction waste accounts for about 25% of the total waste intake at the three existing landfills. If there are insufficient public fill capacity and waste reduction measures being implemented, more public fill would probably be diverted to landfills and the landfill life will be further shortened.
Scientists at the CRC for Contamination Assessment and Remediation of the Environment are using the Australian Synchrotron to develop a way of turning biosolids from urban sewage into a safe nutrient source for farm soils.
Associate Professor Enzo Lombi and Dr Erica Donner, both also affiliated with the University of South Australia, are involved in the project. They aim to make available the phosphorus, nitrogen and potassium from biosolids, as well as organic carbon and micro-nutrients such as copper and zinc. They also want to ensure that toxic metals such as cadmium and lead in biosolids are not able to re-enter the food chain, as their presence is a major obstacle to the widespread reuse of biosolids as soil improvers.
The researchers hope that urban waste can supply nutrients to help maintain the fertility of Australian soils in the face of growing global nutrient scarcities and soaring fertiliser prices.
‘Australia’s sewage works produce more than 300 000 tonnes of biosolids every year, derived from the settling process in primary treatment and the waste bacteria from secondary treatment,’ says Assoc. Prof. Lombi.
‘Most biosolids material is simply stored in huge dumps, where it poses a long-term management issue.’
The team is using the synchrotron to study the chemistry of the bonds that bind toxic metals to particles within the waste. This will enable them to pioneer new ways to bind the metals, preventing their mobility into the environment – a lower-cost solution than separation and removal.
