A considerable contribution to the greenhouse effect originates from landfills. This contribution originates from the degeneration of waste in the landfill. The gas which is created during the degeneration consists of 40 to 60% methane. One mole of methane has a global warming potential which is 28 times higher than that of carbon dioxide. Therefore, emissions of methane should be reduced. One method which can be used to reduce this emission is the oxidization of methane to carbon dioxide. This can be done by the construction
of a cover soil with methanotrophic bacteria in the soil. These bacteria oxidize methane as their source of carbon and energy. This oxidation process discriminates against the heavier isotopes present in the gas, this shifts the isotope signature. A method to determine the oxidation efficiency of the methane is based on the evaluation of this change in isotope signature over the cover soil. Next to the fractionation of isotopes due to oxidation, fractionation also occurs due to diffusion. However, fractionation due to diffusion is generally
assumed to be negligible. Mostly, this assumption is valid, since the dominant part of transport is advective; which does not discriminate against an isotope.

In this thesis the effect of compaction and saturation on two sands are evaluated. Using this evaluation, the criteria during which diffusion becomes an important transport phenomena are determined. This is determined by a series of experiments, where the concentration of methane is monitored while the gas diffuses through a soil sample. In this thesis the effect of the soil matrix on the fractionation of methane is also evaluated. This is evaluated by performing isotope spectrometry on samples of gas, taken at different times during the experiments. These two aspects are combined to evaluate if the oxidation efficiency can still be determined using fractionation of stable methane isotopes when diffusion plays a considerable role in gas transport.

During the experiments the decrease of methane in the chamber was measured. Spread over two soils, for a total of 18 variations in compaction or saturation the decrease of methane over time was measured. The results of the experiments show that for diffusion no distinction between variation in compaction and saturation needs to be made. Compaction and saturation can be described together for both soils using the air-filled porosity. The relation between the air-filled porosity and the effective diffusion coefficient is linear for both soils. Due to the large sand fraction the share of coarse pores is high for the whole range of compaction, meaning that no significant increase of tortuosity is visible in the relation between air-filled porosity and the effective diffusion coefficient. When the effective diffusion coefficients are compared to effective permeability values of these soils, it showed that the diffusion is more important for drier and more compacted soils. Thus, diffusive transport becomes important for gas transport over a cover soil when the pressures are lower, the soil is drier, and the soil is more compacted.

The fractionation factors due to diffusion, which have been determined for a selection of experiments, showed no trend with any other measured parameters. The precision of the measured values from which the fractionation factors are determined is high. Thus, the confidence in the fractionation factors is high.
The lack of a trend present means that in sand the soil matrix has no effect on the fractionation factor. This means that the fractionation factor due to diffusion in soil is the same as in free air. For the calculation of the oxidation efficiency with a relevant diffusive flux the ratio of diffusive to advective flux needs to be
determined but the fractionation factor due to diffusion is constant. Before the oxidation efficiency can be calculated, first the load needs to be corrected for any loss through hot-spots. Next, the advective flux and diffusive flux are combined, this is done by adding the fluxes together. The fluxes can be added because there are no interdependent effects, each flux only increases the total flux. Thus, the oxidation efficiency can be calculated using the changes in isotope signatures, even when a significant diffusive flux is present.

In Sri Lanka, the government and the Liberation Tigers of Tamil Eelam waged a civil war between 1983 and 2009. During this period the social and economic development in the north and east of the country was disrupted. Due to this disruption a development opportunity for this region is the expansion of the fishery industry. In 2016, the Sri Lankan government proposed the Northern Province Sustainable Fisheries Development Project, in which the construction of a harbour at Point Pedro in the Jaffna District is included. This harbour should become the second largest fishery harbour in Sri Lanka.

This report covers the design study of the Point Pedro harbour project, the goal of this study is to design a safe, economically efficient and socially accepted harbour at Point Pedro. To achieve this goal, the following research question “How can safety, economic efficiency and environmental impact be combined optimally in a harbour design for Point Pedro in the Jaffna District?” is answered.

In figure XX, the final design of the harbour can be seen. This design is focused on the optimal combination between safety, economic efficiency and environmental impact. Because these criteria are conflicting, they are prioritized as follows: (1) safety, (2) economic efficiency and (3) environmental impact. Safety is provided by constructing breakwaters around the harbour, providing sheltered water conditions in the harbour basin. Also, the harbour entrance is constructed in a way that monsoon waves cannot directly intrude into the basin. Economic efficiency is accounted for by constructing the quay wall close to the central located fish processing facilities. This optimizes the supply chain, resulting in a smaller loss in the fish production (compared to the current situation). The costs are optimized by reusing all dredged material inside the breakwater or for land reclamation. Additionally, the location of the harbour entrance is minimizing the sailing routes as much as possible, without creating safety issues due to wave intrusion. Finally, the negative effects of social impact are limited by involving local fishermen and residents during the entire development process. Because these stakeholders are potential blockers of the project, it is important to include their opinions in the design. This can also be done by broadening the scope, in which touristic facilities and accommodations can be included in the project. Other negative impacts of the harbour can be either mitigated or minimized. However, because the environmental impact is determined as the least important criteria, it is not able to solve every issue.

This design is considered to be the most optimal combination for the harbour design of Point Pedro, regarding the criteria of safety, economic efficiency and environmental impact. It is recommended to EML Consultants that three characteristics of the proposed design should be implemented in their final design for Point Pedro: (1) apply building on the reef for land reclamation inside the harbour, (2) cluster the fish processing facilities near the unloading quay walls, because it optimizes the fish supply chain and reduces fish loss, and (3) construct the jetties for large boats (in the east of the harbour) as proposed, because it optimizes manoeuverability inside the harbour using minimal space. The final recommendation is to perform additional research to make a more accurate design, as the main limitation of the report is the limited amount of available data. Additional research should be done in the fields of; wave data, ground conditions over the entire harbour basin, cost estimation and sedimentation.