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Domestic (household) biogas plants constitute a growing sub-sector of the anaerobic digestion industry worldwide but have received low interest for improvements. The Chinese dome digester (CDD 1), a major type of domestic biogas plants, is a naturally mixed, unheated and low technology reactor mainly used in rural and pre-urban areas for cooking using animal manure. In this study, a multiphase Computational Fluid Dynamics (CFD) model was applied to evaluate an optimized CDD design and outcomes were compared with results of pilot scale experiments. The optimized digester (CDD2) under goes self-agitating cycles created by the pressure variation from the produced biogas with the aid of a baffle at the top of the reactor, whereas the blank (CDD 1) does not self-agitate. The optimized digester has two pressure zones to improve mixing viz. the self-agitation cycles. The optimized digester is characterized by more, stable and improved hydraulic characteristics and mixing.

Domestic (household) biogas plants constitute a growing sub-sector of the anaerobic digestion industry worldwide but have received low interest for improvements. The Chinese dome digester (CDD 1), a major type of domestic biogas plants, is a naturally mixed, unheated and low technology reactor mainly used in rural and pre-urban areas for cooking using animal manure. In this study, a multiphase Computational Fluid Dynamics (CFD) model was applied to evaluate an optimized CDD design and outcomes were compared with results of pilot scale experiments. The optimized digester (CDD2) under goes self-agitating cycles created by the pressure variation from the produced biogas with the aid of a baffle at the top of the reactor, whereas the blank (CDD 1) does not self-agitate. The optimized digester has two pressure zones to improve mixing viz. the self-agitation cycles. The optimized digester is characterized by more, stable and improved hydraulic characteristics and mixing.

North Sea fisheries are managed by the European Union (EU) through a system of annual quota. Due to uncertainty about future fish stocks, yearly revisions of these policies lead to fluctuation in quota, which in turn affects harvest and investment decisions of fishermen. Determination of quota requires high management costs in terms of obtaining information and negotiations between experts and policy makers. To reduce both quota fluctuation and management costs, the EU has proposed a system of multiannual quota. In this paper we study the effect of multiannual quota on quota volatility and resource rents, while accounting for management costs. We develop a bi-level stochastic dynamic programming model, where at level one, the EU determines the quota that maximizes resource rents. At level two, fishermen decide myopically on their harvest and investment levels, subject to the quota. Results show that policy makers can reduce quota volatility and improve resource rents from the fishery with multiannual quota. Important trade-offs are involved in the accomplishment of these objectives: fish stock and investments become more volatile, which leads to more overcapacity.

North Sea fisheries are managed by the European Union (EU) through a system of annual quota. Due to uncertainty about future fish stocks, yearly revisions of these policies lead to fluctuation in quota, which in turn affects harvest and investment decisions of fishermen. Determination of quota requires high management costs in terms of obtaining information and negotiations between experts and policy makers. To reduce both quota fluctuation and management costs, the EU has proposed a system of multiannual quota. In this paper we study the effect of multiannual quota on quota volatility and resource rents, while accounting for management costs. We develop a bi-level stochastic dynamic programming model, where at level one, the EU determines the quota that maximizes resource rents. At level two, fishermen decide myopically on their harvest and investment levels, subject to the quota. Results show that policy makers can reduce quota volatility and improve resource rents from the fishery with multiannual quota. Important trade-offs are involved in the accomplishment of these objectives: fish stock and investments become more volatile, which leads to more overcapacity.

Met verhoogde ventilatietemperatuur (dode zone) in het voorjaar en de zomer is bij komkommer zonder extra investeringen de productie te verhogen en energie te besparen. Hiermee kan het resultaat met bijna twee euro per vierkante meter worden verhoogd. Ook voor andere vruchtgroentegewassen biedt dit perspectief

Met verhoogde ventilatietemperatuur (dode zone) in het voorjaar en de zomer is bij komkommer zonder extra investeringen de productie te verhogen en energie te besparen. Hiermee kan het resultaat met bijna twee euro per vierkante meter worden verhoogd. Ook voor andere vruchtgroentegewassen biedt dit perspectief