tmoA and related genes encode the alpha-subunit of the hydroxylase component of the major group (subgroup 1 of subfamily 2) of bacterial multicomponent mono-oxygenase enzyme complexes involved in aerobic benzene, toluene, ethylbenzene and xylene (BTEX) degradation. A PCR-denaturing gradient gel electrophoresis (DGGE) method was developed to assess the diversity of tmoA-like gene sequences in environmental samples using a newly designed moderately degenerate primer set suitable for that purpose. In 35 BTEX-degrading bacterial strains isolated from a hydrocarbon polluted aquifer, tmoA-like genes were only detected in two o-xylene degraders and were identical to the touA gene of Pseudomonas stutzeri OX1. The diversity of tmoA-like genes was examined in DNA extracts from contaminated and non-contaminated subsurface samples at a site containing a BTEX-contaminated groundwater plume. Differences in DGGE patterns were observed between strongly contaminated, less contaminated and non-contaminated samples and between different depths, suggesting that the diversity of tmoA-like genes was determined by environmental conditions including the contamination level. Phylogenetic analysis of the protein sequences deduced from the amplified amplicons showed that the diversity of TmoA-analogues in the environment is larger than suggested from described TmoA-analogues from cultured isolates, which was translated in the DGGE patterns. Although different positions on the DGGE gel can correspond to closely related TmoA-proteins, relationships could be noticed between the position of tmoA-like amplicons in the DGGE profile and the phylogenetic position of the deduced protein sequence.
This research contributes to understanding and shaping systems for OFMSW separation at urban Small and Medium Enterprises (SMEs, such as offices, shops and service providers). Separating SMEs’ organic fraction of municipal solid waste (OFMSW) is both an opportunity and a serious challenge for the transition towards circular cities. It is an opportunity because OFMSW represents approximately 40% of the total waste mass generated by these companies. It is challenging because post-collection separation is not feasible for OFMSW. Therefore, SMEs disposing of waste should separate their solid waste so that processing the organic fraction for reuse and recycling is practical and attainable. However, these companies do not experience direct advantages from the extra efforts in separating waste, and much of the OFMSW ends up in landfills, often resulting in unnecessary GHG emissions. Therefore, governments and waste processors are looking for ways to improve the OFMSW separation degree by urban companies disposing of waste through policies for behaviour change.There are multiple types of personnel at companies disposing of waste. These co-workers act according to their values, beliefs and norms. They adapt their behaviour continuously, influenced by the physical environment, events over time and self-evaluation of their actions. Therefore, waste separation at companies can be regarded as a Socio-Technical Complex Adaptive System (STCAS). Agent-based modelling and simulation are powerful methods to help understand STCAS. Consequently, we have created an agent-based model representing the evolution of behaviour regarding waste separation at companies in the urban environment. The model aims to show public and private stakeholders involved in solid waste collection, transport and processing to what extent behaviour change policies can shape the system towards desired waste separation degrees.We have co-created the model with participants utilising literature and empirical data from a case study on the transition of the waste collection system of a business park located at a former harbour area in Amsterdam, The Netherlands. First, a conceptual model of the system and the environment was set up through participatory workshops, surveys and interviews with stakeholders, domain experts and relevant actors. Together with our case participants, five policies that affect waste separation behaviour were included in the model. To model the behaviour of each company worker’s values, beliefs and norms during the separation and disposal of OFMSW, we have used the Value-Belief-Norm (VBN) Theory by Stern et al. (1999). We have collected data on waste collection behaviour and separation rates through interviews, workshops and a literature study to operationalise and validate the model.Simulation results show how combinations of behaviour profiles affect waste separation rates. Furthermore, findings show that single waste separation policies are often limitedly capable of changing the behaviour in the system. Rather, a combination of information and communication policies is needed to improve the separation of OFMSW, i.e., dissemination of a newsletter, providing personal feedback to the co-workers disposing of waste, and sharing information on the (improvement of) recycling rates.This study contributes to a better understanding of how policies can support co-workers’ pro-environmental behaviour for organic waste separation rates at SMEs. Thus, it shows policymakers how to stimulate the circular transition by actively engaging co-workers’ waste separation behaviour at SMEs. Future work will extend the model’s purpose by including households and policies supporting separating multiple waste types aimed at various R-strategies proposed by Potting et al. (2016).
MULTIFILE
