Zoekresultaten

Will implementation of green gas into the gas supply be feasible in the future?

Energy efficiency, greenhouse gas reduction and cost price of a green gas supply chain were evaluated. This supply chain is based on co-digestion of dairy cattle manure and maize, biogas upgrading and injection into a distribution gas grid. A defined reference scenario reflects the current state of practice, assuming that input energy is from fossil origin. Possible improvements of this reference scenario were investigated. For this analysis two new definitions for energy input-output ratio were introduced; one based on input of primary energy from all origin, and one related to energy from fossil origin only. Switching from fossil to green electricity significantly improves the energy efficiency (both definitions) and greenhouse gas reduction. Preventing methane leakage during digestion and upgrading, and re-using heat within the supply chain show smaller improvements on these parameters as well as on cost price. A greenhouse gas reduction of more than 80 % is possible with current technology. To meet this high sustainability level, multiple improvement options will have to be implemented in the green gas supply chain. This will result in a modest decrease of the green gas cost price.

Antarctic cruise tourism: the paradoxes of ambassadorship, "last chance tourism" and greenhouse gas emissions

This paper examines a paradoxical issue in tourism's adaptation to climate change and emissions reduction demands. Operators increasingly take tourists to destinations threatened by climate change, with Antarctica and other polar regions as favourites and cruise ship and aircraft as main transport modes. The selling point is to see a destination before it disappears, a form of last chance tourism. This has been claimed to increase the environmental awareness of tourists and make them "ambassadors" for conservation and the visited destination. Antarctic cruise ship passengers tripled from 2000 to 2007. The paper finds that high levels of greenhouse gas emissions are created by cruise ship tourists in general, and especially high levels for those visiting the Antarctic, up to approximately eight times higher per capita and per day than average international tourism trips. A survey found no evidence for the hypothesis that the trips develop greater environmental awareness, change attitudes or encourage more sustainable future travel choices. Of the Antarctic cruise passengers surveyed, 59% felt that their travel did not impact on climate change; fewer than 7% had or might offset their emissions. Alternative opportunities for visitation to glacial/polar destinations that comply with the desire to reduce future emissions are discussed.

The challenge of implementing green gas into the gas supply

In order to gain a more mature share in the future energy supply, green gas supply chains face some interesting challenges. In this thesis green gas supply chains, based on codigestion of cow manure and maize, are considered. The produced biogas is upgraded to natural gas quality and injected into the existing distribution gas grid and thus replacing natural gas. Literature research showed that relatively much attention has been paid up to now to elements of such supply chains. Research into digestion technology, agricultural aspects of (energy) crops and logistics of biomass are examples of this. This knowledge is indispensable, but how this knowledge should be combined to help understand how future green gas systems may look like, remains a white spot in the current knowledge. This thesis is an effort to fill this gap. A practical but sound way of modeling green gassupply chains was developed, taking costs and sustainability criteria into account. The way such supply chains can deal with season dependent gas demand was also investigated. This research was further expanded into a geographical model to simulate several degrees of natural gas replacement by green gas. Finally, ways to optimize green gas supply chains in terms of energy efficiency and greenhouse gas reduction were explored.

Energy self-sufficiency and sustainability in a defined neighbourhood: Bio-methanation to green gas can outperform green hydrogen

In Europe, green hydrogen and biogas/green gas are considered important renewable energy carriers, besides renewable electricity and heat. Still, incentives proceed slowly, and the feasibility of local green gas is questioned. A supply chain of decentralised green hydrogen production from locally generated electricity (PV or wind) and decentralised green gas production from locally collected biomass and biological power-to-methane technology was analysed and compared to a green hydrogen scenario. We developed a novel method for assessing local options. Meeting the heating demand of households was constrained by the current EU law (RED II) to reduce greenhouse gas (GHG) emissions by 80% relative to fossil (natural) gas. Levelised cost of energy (LCOE) analyses at 80% GHG emission savings indicate that locally produced green gas (LCOE = 24.0 €ct kWh−1) is more attractive for individual citizens than locally produced green hydrogen (LCOE = 43.5 €ct kWh−1). In case higher GHG emission savings are desired, both LCOEs go up. Data indicate an apparent mismatch between heat demand in winter and PV electricity generation in summer. Besides, at the current state of technology, local onshore wind turbines have less GHG emissions than PV panels. Wind turbines may therefore have advantages over PV fields despite the various concerns in society. Our study confirms that biomass availability in a dedicated region is a challenge.

Mitigating tourism's greenhouse gas emissions: a global transport and tourism modelling approach

Tourism and climate change mitigation : methods, greenhouse gas reductions and policies