Biological waste treatment options for Dundee City

Executive summary

The EU landfill Directive sets the targets of biodegradable waste sent to landfill at 35% of the 1995 levels by 2020, for the UK. Scotland, with SEPA as the local authority, has set to reduce the total amount of waste generated and maximise on recovery, recycle and compose 70% of the waste by 2025, and landfill 5% of the waste, through the zero waste plan. This paper thus is a brief that seeks to determine the best suited method for biological waste disposal in DUNDEE city. The determination is done through the Multi-criteria Decision analysis framework with compositing being considered to be the best method because it has stable by-products, it is more-environmentally friendly, and it is socially acceptable.

Table of Contents

Executive summary. 2

1. Introduction. 4

1.1.       Household and similar waste. 5

2. Multi-criteria Decision Analysis (MCD). 6

2.1.       Criterion weighting. 7

2.2.       Aspect analysis. 8

3. Discussion. 8
4. Conclusion. 9
5. References. 10
6. Appendix. 11

1. Introduction

The EU landfill Directive sets the targets of biodegradable waste sent to landfill at 35% of the 1995 levels by 2020, for the UK. To meet the legal requirement set by the Directive, the UK is required to divert about 40% of its household waste from landfill (Friends of the Earth Trust 2002). In 2014, the recycling rate for household waste was at 44.9%, an increase from 44.1% in 2013, and this compares to 40.4% in 2010 (Department for Environment, food & Rural Affairs 2015). The target is to have the UK realize a 50% of recycling rate for household waste by 2020. Biodegradable Municipal Waste (BMW) sent to landfills in the UK, has been on a steady decline with the amount in 2013 being 9.2 million tonnes, a 25% of the 1995 waste amount directed to landfills, which means the UK comfortably met the 2010 BMW landfill target. Waste management is the responsibility of the various local authorities and report to the UK government.

Scotland, with SEPA as the local authority, has set to reduce the total amount of waste generated and maximise on recovery, recycle and compose 70% of the waste by 2025, and landfill 5% of the waste, through the zero waste plan (Department for Environment… 2015). As shown in table 1, the amount of waste generated in Scotland has decreased on average from 2010, even though the 2014 total waste was 2,349,000 tonnes compared to 2,311,000 tonnes, nevertheless, the total of recycled waste has increased from 916,000 tonnes in 2013 to 962,000 in 2014.

Table 1. Waste from Households, Scotland, 2010-14 (Adopted from Department for Environment… 2015)

In Dundee City and as shown in the appendix, the total of household waste generated in 2014 was 46,186 tonnes of which 33,193 tonnes was disposed off through incineration, and 4,394 tonnes directed to landfills (Scotland Environment 2015). The majority of household waste and other organic waste are recyclable and thus, disposal is mainly through compositing, incineration or landfill. Of these methods, incineration and landfill are not environmentally friendly as incineration contributes to green house gasses, and landfill is typical pollution. Organic waste recycled in Dundee City in 2014 was from animal and vegetable waste at 92 tonnes and 6,790 tonnes respectively (Scotland Environment 2015). Mark you, household waste and similar waste is responsible for the bulk of the waste in Dundee City.

• Household and similar waste

Dundee City household and similar waste was at 46,186 tonnes in 2014, the highest of the waste bulk, and it therefore presents the highest potential for recycling, considering there is no recycling done for this segment of the city’s waste. Currently, Dundee has a source-separation scheme for waste collection. Household waste and similar waste contributes 72.5% of the total waste in Dundee and 76% of this waste type has recyclable potential (Department for Environment… 2015). Household waste is mainly mixed in nature with no further separation possible thus, further treatment required. There are a number of treatment methods available for household waste among them biological and thermal methods.  Given the high organic and biodegradable content of this waste, and the harmful consequences of incineration, biological methods of disposal are more beneficial for reduction of the total content weight and increase potential of generation of useful products (Scotland Environment 2015).

Biological waste management methods available for organic waste include anaerobic digestion (AD), residual derived fuel treatment (RDFT), and in-vessel composting (IVC). RDFT method makes use of both mechanical treatment and biological methods. These three methods have their respective advantages and disadvantages and to maximize on the benefits and minimize the disadvantages, a holistic approach referred to as the Best Practical Environmental Option (BPEO) is proposed. BPEO is focused towards protection of the environment, environmental conservation, and other factors among them acceptability and cost.

2. Multi-criteria Decision Analysis (MCD)

This section uses the MCDA to evaluate on various biological waste treatment options and their applicability on waste management in Dundee City. The analysis is based on a set of predetermined factors that are in line with waste reduction strategy and environmental policies applicable in the region.

Government policy: one of the primary reasons for a waste management option is to enable realization of the landfill directive and the set targets. To this end, the best suited waste disposal option is that which allows for greater diversion of landfill i.e. the option with the final weight in kg of waste disposed scores the highest. Government policy bears the highest ranking for is represents the most relevant criteria in the selection of a waste management option for realization of the landfill directive targets (Babalola 2015).

Sustainability: the waste management option selected should be sustainable in terms of its impact to the environment and impact to human health. Impact to the environment encompasses such features as energy efficiency and emissions to the environment. The general objective for diversion of landfill is to reduce environmental impact through greenhouse emissions and as such, the best option is that which is most environmentally friendly. An option with the most impact to the environment and human health is allocated the least score (Babalola 2015).

Waste management cost:  innovation has been voiced as being a gateway towards emission reduction and adaptation, but technology that has high implementation costs is considered to be economically un-feasible, thus the importance of this criteria on the decision analysis tree. For this analysis, the costs and implementation costs as well as any expected revenue have to be determined, for technology with income, the higher the score and the higher the costs, the lower the score (Babalola 2015).

Socio-economics: this is the effect the option has on the society and these effects are measured in terms of employment opportunities generated by the option, and public involvement. Even though public involvement is hard to determined, it is determined through estimation of the interactive effect with the public related to increase or decrease of public interests to partake or/and commit to waste disposal management. This can be through various methods among them, influence on businesses, and acceptability by the public (Babalola 2015).

• Criterion weighting

Table 2. Criteria weighting

Each of the criterion weighting is ranked based on an estimate of a whole, gauged on its relevance and importance towards realization of Dundee’s recycling target. Based on this, government policy is awarded 70% based on its importance in the selection of an option (Santibañez-Aguilar et al. 2013). Aspect rating is ranked on a 10 point ratio based on its importance to the criteria and in table 3; each of the aspects is evaluated on estimates on a scale of 1-5 points and relativity to each other.

• Aspect analysis

Table 3. Aspect analysis

3. Discussion

Waste generated, especially household waste and similar waste, contains a significant amount of recyclables which require pre-treatment before the final disposal technique. Household waste is mainly solid in nature and thus, sorting is an applicable pre-treatment method to rid the lot of the non-biodegradable and hazardous materials. Mechanical screening is also an alternative pre-treatment method to ensure stability of the waste as well as the products (Santibañez-Aguilar et al. 2013).

The best biological treatment method should be suited for the nature and composition of Dundee city waste. RDFT as a biological method doesn’t represent a method that optimizes waste recovery and as such, it is ruled out. The combination of IVC and AD bears costs implications and they don’t have any returns in terms of the produced by-products. On the other hand, AD is a promising option because it has the potential for energy generation, but given the mixed nature of the waste generated in Dundee City, it wouldn’t be a suitable feedback for the process (Santibañez-Aguilar et al. 2013). In addition, the resulting by-product would be of high weight per kg. Compositing presents a larger prospect for the reduction of total weight per kg of the original waste and it consumes less energy, it is sustainable, and socially acceptable compared to AD. Based on the analysis matrix (criterion weighting and aspect analysis), composting is considered to be the best practical environmental option for waste disposal in Dundee city and as an alternative to landfills.

4. Conclusion

The 2014 waste management statistics for the UK is an indication that the country is on target to realizing the 2020 EU landfill diversion directive. Even though the recycling rate of Dundee City was on 10% in 2014, there is a huge potential for increasing this rate mainly with focus to the household and similar waste through biological waste disposal methods. To enhance realization of the zero landfill plans, the waste disposal method adopted should ensure the resultant by-products are usable and are in line with the analysis matrix. Compositing has been recommended as the best suited biological method for disposing Dundee City waste. The method produces by-products that are stable, it is more-environmentally friendly compared to the others, and it is socially acceptable thus encourages members to partake in waste management.

5. References
6. Babalola M.A., 2015. A Multi-Criteria Decision Analysis of Waste Treatment Options for Food and Biodegradable Waste Management in Japan, Environments, 2, 471-488; doi:10.3390/environments2040471
7. Department for Environment, food & Rural Affairs, 2015. UK Statistics on Waste. Available at https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/487916/UK_Statistics_on_Waste_statistical_notice_15_12_2015_update_f2.pdf accessed on 21 February 2016
8. Friends of the Earth Trust, 2002. Fact Sheet: EU Landfill Directive and Waste Strategy. [Online] Available at:
9. http://www.foe.co.uk/sites/default/files/downloads/eu_landfill_directive.pdf accessed 21 February 2016
10. Santibañez-Aguilar J.E, Ponce-Ortega, J.M, Betzabe González-Campos J, Serna-González M, & El-Halwagi M.M, 2013. Optimal planning for the sustainable utilization of municipal solid waste. Waste Manag., 33, 2607–2622.
11. Scotland Environment, 2015. Summary data on Scottish household waste generation and management. Available at http://www.environment.scotland.gov.uk/get-interactive/data/household-waste/ accessed on 20 February 2016

6. Appendix

Figure 1. Waste type (local authority) in Dundee city in Scotland in 2014 (adapted from Scotland Environment, 2015)