• Energy Research

Abstract This paper has two key objectives. Firstly, using the findings from case study research undertaken in Colombo (Sri Lanka), Faisalabad (Pakistan) and Dar es Salaam (Tanzania), the paper seeks to demonstrate the importance of an appropriate regulatory framework and effective mechanisms of enforcement for sustainable urban transport systems in developing countries. Secondly, the paper highlights the critical importance of communication and co-ordination between stakeholders (defined here as transport users, providers and regulators) if regulation is to be effective. The views of poor and disadvantaged passenger groups—women, children, the elderly and disabled—are used in the paper to illustrate the importance of transport systems to their livelihoods, such as work, education, health and social pursuits. The case studies suggest that in the context of the failure of both the fully regulated public transport sector and the completely deregulated sector self regulation is a potentially useful alternative. In practice, self regulation has been achieved in the case study locations through the formation of cooperatives or associations of stakeholders such as users and operators. In the conclusion, the paper makes two key points. Firstly, that regulation must be open, honest and effective, but not so detailed or ‘heavy’ that it incites the potential for corrupt practices. Secondly, communication and co-ordination between stakeholders is critical if any form of regulation is to be effective—owners', employees' and passengers' associations have a vital role in this regard, as do Transport Forums consisting of all stakeholders. The participation of stakeholders and real and effective consultation are more important in the case of self regulation of public transport service provision than in other regulatory regimes.

Abstract Current ways of managing spent coffee grounds (SCGs) are uneconomical and have significant environmental impacts. Alternative approaches, such as hydrothermal carbonisation (HTC), which can utilise their rich organic matter for energy recovery purposes are essential. Here we present, a response surface methodology (RSM) for understanding the combined interactive effects due to the main HTC operating conditions, i.e. reaction temperature and residence time, as well as optimising them to produce hydrochar from SCGs of maximal yield and calorific value. The fuel properties and combustion behaviours of hydrochar were further evaluated to assess its suitability to replace coals for energy applications. Depending on the operating conditions, the atomic carbon content and calorific values of the hydrochar were significantly improved: by 11.2–30.7% and 15.8–44.7% respectively. The highest hydrochar calorific value recorded, 33.5 MJ kg−1, resembled that of anthracite and dry steam coal, generally used in the UK. At optimal conditions of ∼216 °C and 1hr - guided by the RSM - a maximal hydrochar yield of ∼64% and a calorific value of 31.6 MJ kg−1 are feasible. Using this as a benchmark, the 500,000 tonnes of SCGs generated annually in the UK has the potential of replacing 4.4% of the coal used for electricity generation in the country.

Abstract Decomposition kinetics of primary sewage sludge (PSS) and synthetic faeces (SF), of various moisture contents, were investigated over different reaction times and temperatures using a hydrothermal batch reactor. Solid decomposition of PSS and SF was first-order with activation energies of 70 and 78 kJ/mol, and pre-exponential factors of 4.0 × 106 and 1.5 × 107 min−1, respectively. Solid decomposition was significantly affected by reaction temperature more so than reaction time. Higher temperature resulted in higher solids conversion to hydrochar. Equilibrium solid hydrochar yields (relative to the original dry mass used) were 74%, 66%, 61% and 60% for PSS at 140, 170, 190 and 200 °C respectively, and 85%, 49%, 48% and 47% for SF at 140, 160, 180 and 200 °C respectively. Energy contents of the hydrochars from PSS carbonised at 140–200 °C for 4 h ranged from 21.5 to 23.1 MJ/kg, and increased following carbonisation. Moisture content was found to affect the Hydrothermal Carbonisation (HTC) process; feedstocks with higher initial moisture content resulted in lower hydrochar yield and the extent of carbonisation was more evident in feedstock with lower moisture content. The results of this study provide information useful for the design and optimisation of HTC systems for waste treatment.

European countries are introducing changes to their legislation and institutions that enable infrastructure procurement through public–private partnerships (PPPs). The purpose of this paper is to survey the legislation and institutions for infrastructure procurement through PPPs across Europe. Procurement procedures have no defined status in the regulatory framework of the European Union (EU); as a consequence, each member state has developed its own PPP legal and institutional framework. As such the process of procurement varies widely between the member states. The legislative frameworks for PPPs are discussed with reference to central and eastern Europe. This paper finds that effective legal, regulatory and contractual conditions perform successfully when they are based on and supported by the institutional framework of a country. A majority of European countries have realised this necessity and have developed various institutional framework models accordingly. These models are defined according to the degree of centralisation of PPP institutions in a country's overall state structure; the models are: highly centralised (western newly independent states); highly decentralised (France and Portugal); and mixed centralised and decentralised (Ireland, the UK, Italy and the Netherlands). The changing institutional framework in new member states is described with reference to the Czech Republic, Hungary and Poland.

Microwave hydrothermal carbonization (M-HTC) is reported in this study as a viable sanitation technology that can reliably overcome the heterogeneous nature of human faecal biowaste (HBW) and realize its intrinsic energy value. Solid chars produced from the M-HTC process at 180°C and 200°C were characterized to further the understanding of the conversion pathways and their physicochemical, structural and energetic properties. The study revealed solid chars recovered were predominantly via a solid-solid conversion pathway. In terms of yield, more than 50% of solid chars (dry basis) can be recovered using 180°C as a benchmark. Additionally, the carbonized solid chars demonstrated enhanced carbon and energy properties following the M-HTC process: when compared to unprocessed HBW, the carbon content in the solid chars increased by up to 52%, while the carbon densification factor was greater than 1 in all recovered chars. The calorific values of the chars increased by up to 41.5%, yielding heating values that averaged 25MJ.kg-1. Thermogravimetric studies further revealed the solid fuel chars exhibited greater reactivity when compared with unprocessed HBW, due to improved porosity. This work strengthens the potential of the M-HTC sanitation technology for mitigating poor sanitation impacts while also recovering energy, which can complement domestic energy demands.

© 2014 Elsevier Ltd.The Nigerian government proposed the use of compressed natural gas (CNG) as an automotive fuel in 1997 as part of the initiatives to harness natural gas (NG) resources but progress has been slow. This paper examines the natural gas vehicle (NGV) implementation approaches and outcomes in seven countries with diverse experiences in order to gain an understanding of the barriers to the NGV market development in Nigeria. The analysis employs hermeneutic principles to secondary data derived from academic literature, published reports from a variety of international agencies, grey literature, and text from online sources and identifies eight success factors for NGV market development namely: strategic intent, legal backing, learning and adaptation, assignment of responsibilities, financial incentives, NG pricing, consumer confidence, and NG infrastructure. The paper concludes that the principal impediment to NGV market development in Nigeria is the uncoordinated implementation approach and that greater government involvement is required in setting strategic goals, developing the legal and regulatory frameworks, setting of clear standards for vehicles and refuelling stations as well as assigning responsibilities to specific agencies. Short-term low cost policy interventions identified include widening the existing NG and gasoline price gap and offering limited support for refuelling and retrofitting facilities.

This paper compares conventional and microwave hydrothermal carbonization (HTC) of human biowaste (HBW) at 160 °C, 180 °C and 200 °C as a potential technology to recover valuable carbonaceous solid fuel char and organic-rich liquor. Also discussed are the influence of HTC heating methods and temperature on HBW processing conversion into solid fuel char, i.e. yield and post-HTC management, dewaterability rates, particle size distribution and the carbon and energy properties of solid fuel char. While HTC temperatures influenced all parameters investigated, especially yield and properties of end products recovered, heating source effects were noticeable on dewatering rates, char particle sizes and HBW processing/end product recovery rate and, by extension, energy consumed. The microwave process was found to be more efficient for dewatering processed HBW and for char recovery, consuming half the energy used by the conventional HTC method despite the similarity in yields, carbon and energy properties of the recovered char. However, both processes reliably overcame the heterogeneity of HBW, converting them into non-foul end products, which were easily dewatered at <3 seconds/g total solids (TS) (c.f. 50.3 seconds/g TS for a raw sample) to recover energy-densified chars of ≈17 MJ/kg calorific value and up to 1.4 g/l of ammonia concentration in recovered liquor.

The Millennium Development Goals (MDGs) on drinking water were reported to have been achieved five years earlier than the target date of 2015 in all the continents, except Africa and Oceania. This study assessed the performance of selected state water utilities in Nigeria in Africa over a period of years to determine improvements, if any, in their service coverage and demand gap in meeting the ambitious SDG target 6.1, which aims to achieve sustainable drinking water for all by 2030. Employing the key performance indicator (KPI) methodology, encompassing operational and maintenance efficiency, investment efficiency, and financial sustainability, this research unveils a widening disparity between water supply and demand gap. Alarming is the revelation that the revenue from water sales falls short of covering operation and maintenance costs, rendering these utilities financially unsustainable. This underperformance of state water utilities signals a formidable barrier to Nigeria’s prospects of attaining the Sustainable Development Goal (SDG) target 6.1, thereby jeopardizing the nation’s ability to ensure universal and affordable access to safe drinking water by 2030.