Recycling of EPS Foam Packaging

Municipalities and organisations are facing a growing problem in disposal and recycling of EPS foam packaging and products. EPS foam (Encapsulated Poly-Styrene) packaging is a highly popular plastic packaging material which finds wide application in packaging of food items, electronic goods, electrical appliances, furniture etc due to its excellent insulating and protective properties. EPS foam (also known as polystyrene) is also used to make useful products such as disposable cups, trays, cutlery, cartons, cases etc. However, being large and bulky, polystyrene take up significant space in rubbish bins which means that bins becomes full more quickly and therefore needs to be emptied more often.

Polystyrene is lightweight compared to its volume so it occupies lots of precious landfill space and can be blown around and cause a nuisance in the surrounding areas. Although some companies have a recycling policy, most of the polystyrene still find its way into landfill sites around the world.

Environmental Hazards of EPS Foam

While it is estimated that EPS foam products accounts for less than 1% of the total weight of landfill materials, the fraction of landfill space it takes up is much higher considering that it is very lightweight.  Furthermore, it is essentially non-biodegradable, taking hundreds perhaps thousands of years to decompose.

Even when already disposed of in landfills, polystyrene can easily be carried by the wind and litter the streets or end up polluting water bodies. When EPS foam breaks apart, the small polystyrene components can be eaten by marine organisms which can cause choking or intestinal blockage.

Polystyrene can also be consumed by fishes once it breaks down in the ocean.  Marine animals higher up the food chain could eat the fishes that have consumed EPS, thus concentrating the contaminant.  It could be a potential health hazard for us humans who are on top of the food chain considering that styrene, the plastic monomer used in manufacturing EPS has been classified by the US National Institutes of Health (NIH) and the International Agency for Research on Cancer (IARC) as a possible human carcinogen.

Styrene is derived from either petroleum or natural gas, both of which are non-renewable and are rapidly being depleted, creating environmental sustainability problems for EPS.

Trends in EPS Foam Recycling

Although the Alliance of Foam Packaging Recyclers have reported that the recycling rate for post-consumer and post-commercial EPS in the United States have risen to 28% in 2010 from around 20% in 2008, this value is still lower than most solid wastes.  According to USEPA, auto batteries, steel cans and glass containers have recycle rates of 96.2%, 70.6% and 34.2% respectively.

Because it is bulky, EPS foam takes up storage space and costs more to transport and yet yields only a small amount of polystyrene for re-use or remolding (infact, polystyrene accounts for only 2% of the volume of uncompacted EPS foams). This provides little incentive for recyclers to consider EPS recycling.

Products that have been used to hold or store food should be thoroughly cleaned for hygienic reasons, thus compounding the costs.  For the same reasons, these products cannot be recycled to produce the same food containers but rather are used for non-food plastic products.  The manufacture of food containers, therefore, always requires new polystyrene.  At present, it is more economical to produce new EPS foam products than to recycle it, and manufacturers would rather have the higher quality of fresh polystyrene over the recycled one.

The cost of transporting bulky polystyrene waste discourages recyclers from recycling it.  Organizations that receive a large amount of EPS foam (especially in packaging) can invest in a compactor that will reduce the volume of the products. Recyclers will pay more for the compacted product so the investment can be recovered relatively easier.

There are also breakthroughs in studies concerning EPS recycling although most of these are still in the research or pilot stage.  Several studies have found that the bacteria Pseudomonas putida is able to convert polystyrene to a more biodegradable plastic.  The process of polystyrene depolymerization – converting polystyrene back to its styrene monomer – is also gaining ground.

Anaerobic Digestion of Animal Manure

Animal manure is a valuable source of nutrients and renewable energy. However, most of the manure is collected in lagoons or left to decompose in the open which pose a significant environmental hazard. The air pollutants emitted from manure include methane, nitrous oxide, ammonia, hydrogen sulfide, volatile organic compounds and particulate matter, which can cause serious environmental concerns and health problems. In the past, livestock waste was recovered and sold as a fertilizer or simply spread onto agricultural land. The introduction of tighter environmental controls on odour and water pollution means that some form of waste management is necessary, which provides further incentives for biomass-to-energy conversion.

Anaerobic digestion is a unique treatment solution for animal manure as it can  deliver  positive  benefits  related  to  multiple  issues,  including  renewable  energy,  water pollution, and air emissions. Anaerobic digestion of animal manure is gaining popularity as a means to protect the environment and to recycle materials efficiently into the farming systems. Waste-to-Energy (WTE) plants, based on anaerobic digestion of cow manure, are highly efficient in harnessing the untapped renewable energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific gases.

The establishment of anaerobic digestion systems for livestock manure stabilization and energy production has accelerated substantially in the past several years. There are thousands of digesters operating at commercial livestock facilities in Europe, United States,  Asia and elsewhere. which are generating clean energy and fuel. Many of the projects that generate electricity also capture waste heat for various in-house requirements.

Important Factors

The main factors that influence biogas production from livestock manure are pH and temperature of the feedstock. It is well established that a biogas plant works optimally at neutral pH level and mesophilic temperature of around 35o C. Carbon-nitrogen ratio of the feed material is also an important factor and should be in the range of 20:1 to 30:1. Animal manure has a carbon – nitrogen ratio of 25:1 and is considered ideal for maximum gas production. Solid concentration in the feed material is also crucial to ensure sufficient gas production, as well as easy mixing and handling. Hydraulic retention time (HRT) is the most important factor in determining the volume of the digester which in turn determines the cost of the plant; the larger the retention period, higher the construction cost.

Process Description

The fresh animal manure is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable-capacity anaerobic digesters where stabilization of organic waste takes place.

In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.

Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur. Biogas can be used as domestic cooking, industrial heating, combined heat and power (CHP) generation as well as a vehicle fuel. The digested substrate is passed through screw presses for dewatering and then subjected to solar drying and conditioning to give high-quality organic fertilizer.

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