Kingsley L. Iroba

Pretreatment of Lignocellulosic Biomass Using Microorganisms: Approaches, Advantages, and Limitations

Much of Earth’s recent geologic history is dominated by periods of extensive glaciation, with relatively low global mean temperatures and correspondingly low atmospheric CO2 concen‐ trations [1]. The current interglacial period stands out as an anomaly because the atmospheric CO2 concentration has risen sharply above the range of approximately 180-280 parts per million by volume that has defined the past 420,000 years to reach levels that are nearly 40% higher than the biosphere has experienced over this time frame [2]. This rapid increase in CO2 concentration is primarily due to the release of ancient fixed atmospheric CO2 into the modern atmosphere through the combustion of fossil fuel resources over the past 200 years. Since it is clear from ice core records that atmospheric CO2 concentration has a strong positive correlation to global temperature, it is expected that changes to global climate are forthcoming [3]. There are substantial uncertainties regarding the ability of terrestrial and oceanic carbon sinks to absorb this anthropogenic CO2 on time scales that are relevant to human society [2], so the continued release of ancient CO2 into the modern atmosphere at current rates carries with it an important risk of inducing climate changes of unknown amplitude along with a host of ancillary changes that are difficult to predict with certainty. This has led to the search for alternatives to fossil fuels to meet a rising global energy demand, and one such option is the use of extant organic matter to produce energy. This resource contains carbon that was fixed from the modern atmosphere, which means it does not result in a net increase in atmospheric CO2 upon combustion.

Densification of Radio Frequency Pretreated Lignocellulosic Biomass Barley Straw

The present investigation is vital for logistic and costs improvement of lignocellulosic biomass for energy production. In this study, radio-frequency (RF)-based dielectric heating technique was used in the alkaline (NaOH) pretreatment of lignocellulosic biomass (barley straw), so as to enhance the breakdown and accessibility of the cross-linking binding lignin. Three levels of temperature (70oC, 80oC, and 90oC), five levels of ratio of biomass to NaOH solution (1:4, 1:5, 1:6, 1:7, & 1:8), 1 h equilibration time, screen size of 1.6 mm, 1% NaOH concentration, and 20 min residence time were used for the radio frequency pretreatment. The effect of radio frequency pretreatment was assessed through densification of the pretreated and non-pretreated biomass samples. It was observed that the use of NaOH solution and the ratio of biomass to NaOH solution played a major role in the breakdown of the lignified matrix, as well as in the production of pellets with good quality physical characteristics. However, the use of NaOH increased the ash content of the biomass. Washing of the pretreated sample with tap water decreased the ash content, but reduced the quality of the produced pellets.