Biomethane production from grass silage: laboratory assessment to maximise yields

On-farm biogas production is typically associated with forage maize as the biomass source. Digesters are designed and operated with the focus of optimising the conditions for this feedstock. Thus, such systems may not be ideally suited to the digestion of grass. Ireland has ca. 3.85 million ha of grassland. Annual excess grass, surplus to livestock requirements, could potentially fuel an anaerobic digestion industry. Biomethane associated with biomass from 1.1 % of grassland in Ireland, could potentially generate over 10 % renewable energy supply in transport. This study aims to identify and optimise technologies for the production of biomethane from grass silage. Mono-digestion of grass silage and co-digestion with slurry, as would occur on Irish farms, is investigated in laboratory trials. Grass silage was shown to have 7 times greater methane potential than dairy slurry on a fresh weight basis (107 m3 t-1 v 16 m3 t-1). However, comprehensive trace element profiles indicated that cobalt, iron and nickel are deficient in mono-digestion of grass silage at a high organic loading rate (OLR) of 4.0 kg VS m-3 d-1. The addition of a slurry co-substrate was beneficial due to its wealth of essential trace elements. To stimulate hydrolysis of high lignocellulose grass silage, particle size reduction (physical) and rumen fluid addition (biological) were investigated. In a continuous trial, digestion of grass silage of <1 cm particle size achieved a specific methane yield of 371 L CH4 kg-1 VS when coupled with rumen fluid addition. The concept of demand driven biogas was also examined in a two-phase digestion system (leaching with UASB). When demand for electricity is low it is recommended to disconnect the UASB from the system and recirculate rumen fluid to increase volatile fatty acid (VFA) and soluble chemical oxygen demand (SCOD) production whilst minimising volatile solids (VS) destruction. At times of high demand for electricity, connection of the UASB increases the destruction of volatiles and associated biogas production. The above experiments are intended to assess a range of biogas production options from grass silage with a specific focus on maximising methane yields and provide a guideline for feasible design and operation of on-farm digesters in Ireland.

Depression and 'crises of meaninglessness' in the political-economic theology of the money-God

The thesis starts with a historical analysis of the development of depression as a concept. Through this inquiry, the controversies behind the apparent consensus about depression’s etiology and treatment are illuminated, suggesting that the understanding of the climbing rates of depression in contemporary Western civilization is still up for grabs. That’s what the thesis sets out to investigate. In order to accomplish this aim, the study builds upon the classical accounts of Georg Simmel, Émile Durkheim and the more contemporary ideas of Dany-Robert Dufour, in dialogue with an array of supplementary theoretical sources. Navigating through this ‘sea’ of extraordinary and different theories, a new avenue of reflections arises, contributing for the sophistication of the questions made about the phenomenon of depression’s rates. The fundamental argument emerging from this theoretical undertaking is that ‘crises of meaninglessness’ that pervade the collective body of Western contemporary societies have, as one of its consequences, the expansion of depression rates. Meaninglessness in contemporary times is the primary object of investigation of the thesis. The concept, in the context of this study, is not understood as merely an effect of the historical decline of shared social norms due to processes of individualization. Rather, it is claimed, it originates from and is reinforced by the ‘political-economic theology of neo-liberalism’ which becomes virtually generalized in the West, erecting money as a God. The study concludes that by undermining culturally established values, ideals, institutions and principles that may block the dissemination of commodities this new transcendence has been challenging the task of signifying life, potentializing – among other subjective difficulties – the diffusion of depression.