Degradation of excavated polyethylene and polypropylene waste from landfill

In 2016, it was estimated that 7.4 million tonnes of plastic waste have been disposed in landfill in Europe. This waste represents an important opportunity for resource recovery through enhanced landfill mining consistent with recent Circular Economy initiatives. However, a recent review found a lack of data describing the degradation of excavated plastic waste and the potential impact on recycling products such as pyrolysis oil. In this study, the physicochemical characteristics of the main plastic types found in landfills and their implications for recovery and recycling were investigated using a combination of scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Loss of gloss was visually detected for the buried plastic waste samples (polyethylene (PE) and polypropylene (PP)) compared to fresh plastic samples. The SEM-EDS analysis further showed that oxygen was the main element related to the plastic surface alteration. The carbonyl index (CI) of plastic samples buried for >10 years was between 1.5 and 2 times higher than 10 years) was 2 times higher than the fresh and < 10 years samples. Based on these findings, tertiary recycling, such as pyrolysis, seems to be a convenient route for upcycling of recovered plastics from municipal solid waste landfills

Developing the case for enhanced landfill mining in the UK

Across the UK there are around 22,000 landfills sites, suggesting a significant opportunity for recovering value from previously discarded materials. Enhanced landfill mining (ELFM) has been identified as a concept to recover value from landfills through optimized valorization of the resources extracted. This approach, including waste-to-energy (WtE), waste-to-material (WtM) and waste-to-land (WtL) options can also assist in addressing critical and secondary raw material demands and scarcity. However, to date, there is still limited evidence on this potential. In this paper, the results of 9 UK landfill sites characterization and feasibility studies for ELFM are presented. Waste characterisation from 9 landfill sites located in the UK was carried out. Overall 36 core drills and 118 unique waste samples were analysed. High volumes of fines (soil-like) organic material were observed across all samples and significant levels of valuable metals were observed in this fraction. Previous work had determined significant aluminium and copper are contained in the soil-like fines fraction, which does not include the separate metals fraction (i.e. aluminium cans, copper wires etc). At one site the combustible fraction was assessed as a potential refuse-derived fuel [RDF]. Typically, 10-40% by weight of the samples at this site were ‘combustible’, with an average gross calorific value of 12.9 MJ/kg. Plastics extracted from the sites are contaminated and degraded, therefore further work is required to understand the extent of degradation and to assess available options upcycle these materials

Characterisation of excavated plastics for thermochemical upcycling to platform chemicals and liquid fuels

In Europe there are ~500,000 landfills; plastics represent a consistent and significant proportion of waste in landfill (typically 5-25% w/w). This fraction remains in the landfill, along with other non-biodegradable materials, long after the readily biodegradable organics have degraded. During storage in landfill the plastics physicochemical structure is likely to change because of the occurrence of chemical and biochemical reactions, which can lead to their degradation. For instance, H2S and organic acids produced during the acetogenesis phase of landfill are known to degrade plastics, therefore it can be hypothesised that plastics excavated from landfill are not suitable for conventional recycling. The fate of plastics in landfill has not been largely investigated and limited data exists addressing the changes in chemical and physical properties. The aim of this work is to investigate the degradation of plastics in landfill by characterising chemical and physical properties of samples excavated from different landfill depths. Waste samples were extracted from landfills across the UK at depths of 5-40 m. These were sorted in order to determine the total plastic content and the percentage of each type of plastic present (i.e. PET, HDPE etc). The types of plastics were identified using near infrared [NIR] spectroscopy. The surface properties of the excavated plastics were characterised using SEM/EDS to analyse and evaluate their degradation and contamination levels. Chemical characterisation of each plastic fraction has been carried out by proximate and ultimate analyses. Finally, the surface contamination (metal content) of the plastics was determined by ICP. Fresh, non-landfilled, plastic samples matching the plastic types of those found in landfill were characterised for comparison. The data highlighted plastic type variation across the samples, largely dependent on the age of the excavated material. The extent of degradation, was found to depend on the type of plastic and depth of the sample. This work contributes to address the potential utilisation of excavated plastics, such as for upcycling to platform chemicals and/or liquid fuels through thermochemical conversion

Physico-chemical properties of excavated plastic from landfill mining and current recycling routes

In Europe over 5.25 billion tonnes of waste has been landfilled between 1995 and 2015. Among this large amount of waste, plastic represents typically 5–25 wt% which is significant and has the potential to be recycled and reintroduced into the circular economy. To date there is still however little information available of the opportunities and challenges in recovering plastics from landfill sites. In this review, the impacts of landfill chemistry on the degradation and/or contamination of excavated plastic waste are analysed. The feasibility of using excavated plastic waste as feedstock for upcycling to valuable chemicals or liquid fuels through thermochemical conversion is also critically discussed. The limited degradation that is experienced by many plastics in landfills (>20 years) which guarantee that large amount is still available is largely due to thermooxidative degradation and the anaerobic conditions. However, excavated plastic waste cannot be conventionally recycled due to high level of ash, impurities and heavy metals. Recent studies demonstrated that pyrolysis offers a cost effective alternative option to conventional recycling. The produced pyrolysis oil is expected to have similar characteristics to petroleum diesel oil. The production of valuable product from excavated plastic waste will also increase the feasibility of enhanced landfill mining projects. However, further studies are needed to investigate the uncertainties about the contamination level and degradation of excavated plastic waste and address their viability for being processed through pyrolysis

Upcycling of plastics recovered from enhanced landfill mining through pyrolysis.

Since 1950 the global plastics production increased at a compound annual growth rate (CAGR) of about 8.5 % and it is expected to grow in the next 5 years at a CAGR of about 4 %. The estimated amount of plastics that ended up in landfill and natural environment in the past 70 years is 4.9 billion tonnes. Most of this comprises of thermoplastics which can be potentially recycled and reintroduced in the new circular plastic economy reducing the use of virgin fossil resources. To achieve this, more information is needed on recovered plastics physico-chemical characteristics and their suitability for conventional recycling processes. Due to the expected contamination and degradation of excavated plastics, potential upcycling routes need to be explored to produce marketable products. The plastic recycling, fresh waste or excavated, needs to fit into the circular economy strategy which aims to maximise service life and minimise waste. In the case of recovered plastics, the starting material is unused and must be renovated to become useful again. Between common recycling routes for fresh plastic waste, chemical recycling was found in line with the circular economy concept. Specifically, the pyrolysis method leads to the production of chemical compounds that can be used in the plastic industry. This PhD investigates the feasibility of producing valuable products from the pyrolysis of excavated plastics from municipal solid waste (MSW) landfill. Firstly, the physico-chemical characteristics of genuine plastic from landfills were analysed. The chemical and mechanical properties of buried plastics were hypothesised to be affected by the chemical, biochemical and physical parameters within a landfill environment. Secondly, the potential valuable products from the pyrolysis of recovered plastics were investigated. Polyethylene and polypropylene represented 64 wt% of total recovered plastics. The samples with storage of more than 10 years in landfill showed a general greater extent of degradation compared to newer samples. The pyrolysis of excavated plastics at 500°C and 650°C produced the highest level of hydrocarbons and most of the pyrolysis products fitted within the naphtha range (C6-C10) which has a high potential to be used in the petrochemical cluster. The findings from this PhD bring to the attention that buried plastics have hidden potential. These plastics have, in the past, been considered useless by virtue of being landfilled and are potentially harmful to the environment and ecosystem long-term in closed landfill sites. This work demonstrates the potential of recovering value from excavated plastics as part of an enhanced landfill mining project, reducing the need for virgin fossil fuel, preventing long-term pollutants release and producing valuable and useful products.PhD in Energy and Powe

CORD_Data paper_Pyrola.xlsx

Complete dataset of Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), which was used to analyse the pyrolysis decomposition products of 10 plastic samples made up of fresh and excavated samples of different ages from 4 MSW landfill sites. The samples included a single polymer for fresh and excavated polyethylene (PE) and polypropylene (PP), and two types of mixed excavated plastic materials, sample A (PE, PP, polystyrene (PS)) and sample B (PE, PP, PS, polyethylene terephthalate (PET), polyvinyl chloride (PVC)).DTP 2016-2017 Cranfield Universit

CORD_ASPEN Plus paper.xlsx

Complete dataset of ASPEN Plus modelling of pyrolysis of plastic wastes (polyethylene, PE, and polypropylene, PP) recovered from enhanced landfill mining. The ASPEN Plus simulation model was validated with published data and used for predicting possible outputs from the pyrolysis of excavated PE and PP. The model predicted oil yields within 4% error.EP/N509450/

Data for the paper "Degradation of excavated polyethylene and polypropylene waste from landfill"

Degradation of excavated polyethylene and polypropylene waste from landfill, including composition and chemical characterisation.EP/N509450/

Landfill mining report_2016.pdf

An era of rising consumption has led to resource scarcity across major industries. One way to overcome this challenge and ascertain future supply of resources is recovery of landfilled material. This so-called landfilled mining may valorise previously discarded material streams for a number of purposes and contribute to a circular economy. Across England and Wales, there are more than 20,000 landfill sites of which 90% have been closed before 1996. Besides the general belief that valuable resources can be found within landfills, mining the waste has a number of additional benefits. One stems from the fact that they often lack modern environmental protection technology, which may lead to negative environmental and health impacts. The combination of these facts poses an interesting opportunity for combined resource-recovery and remediation strategies. The report at hand is in place to assess viability and feasibility of landfill mining processes across England and Wales in a step-wise approac

Foxes provide a direct dispersal service to Phoenician junipers in Mediterranean coastal environments: ecological and evolutionary implications

Background and aims – Exploring the role of mammalian carnivores as seed dispersers in Mediterranean environments is crucial for understanding biotic interactions and preserving mutualistic networks in areas with high biodiversity. We examine the potential role of the Sardinian fox ( Vulpes vulpes subsp. ichnusae ) as a seed-disperser of two juniper species ( Juniperus phoenicea subsp. turbinata and J. oxycedrus subsp. macrocarpa ) in Mediterranean coastal environments.Methods – Observational and manipulative experiments were conducted in five coastal sites in north-western Sardinia (Italy) between 2010 and 2013.Key results – We found that Sardinian fox actively disperses seeds of J. phoenicea subsp. turbinata, whereas no evidence was obtained for the fox dispersing seeds of J. oxycedrus subsp. macrocarpa. Fox scat contained, on average, 73–86 J. phoenicea subsp. turbinata seeds, accounting 16.3–17.8 % of the average dung weight. The role of Sardinian fox as a primary disperser of J. phoenicea subsp. turbinata is by directly dispersing juniper seeds (via defecation) to a specific microhabitat (i.e. 80–90 % of dung was released on dwarf plants, mainly Helichrysum italicum subsp. microphyllum ), which positively affected the survival of emerged seedlings). We quantified that fox dispersed 30 to 100 seeds per day per hectare (3 500–10 500 seeds per hectare in one winter season).Conclusions – We reported that Sardinian fox is a direct disperser of J. phoenicea subsp. turbinata, thus playing a major role in secondary successional dynamics in Mediterranean coastal environments. Evolutionary implications are discussed, in that the positive interaction between Sardinian fox and J. phoenicea subsp. turbinata could be recent, following the introduction of fox to the Tyrrhenian islands during the 7 th –6 th millennium BC