Synergetic Physical Freezing and Chemical Pretreatment of Lignocellulosic Sugarcane Bagasse Followed by Enzymatic Hydrolysis

This study focuses on employing an eco-friendly pretreatment approach for lignocellulosic Sugarcane Bagasse (SCB) as a major problematic solid waste in Egypt, complying with the standard legislation as well. The applied technique depended on SCB physical fractionation via freezing, followed by chemical hydrolysis using alkaline hydrogen peroxide (AHP) and enzymatic hydrolysis. The changes occurred in macrostructure and the entire lignocellulosic compounds during the pretreatment stages were evaluated. Freezing fractionation resulted in relatively low glucose yield and saccharification ratio at -20°C for 2 h of 307.52 mg/gm native SCB and 48.5%, respectively, where no total reducing sugars (TRS) was obtained. Further AHP pretreatment was performed for the frozen-fractionated SCB at -20°C and 2 h with assistance of Box–Behnken Design response surface methodology (RSM). The investigated key parameters were H2O2 concentration (3, 5.5 and 8 %v/v), temperature (25, 42.5 and 60°C) and pretreatment duration (1, 3 and 5 h). The results revealed that the statistical modelling was able to predict the response of glucose yield and TRS production with R2 = 0.8221 and 0.8814, respectively. Applying the optimization tool of RSM, the optimum predicted values of glucose yield and TRS production were (886.51 mg/gm native SCB and 1.44 mg/mL), respectively; confirmed by the experimental analysis (898.5 mg/gm native SCB and 1.32 mg/mL), respectively. The coincided saccharification ratio was 97.5%. These results were obtained at H2O2 of 3 % (v/v), 56.93°C and 1 h which were 4.32 and 2.01 times higher than that obtained during the freezing pretreatment phase for glucose yield and saccharification ratio, respectively.

An over-used ocean island coastal aquifer, Tenerife (Spain) – tracing inputs for improved resource management

<p>The island of Tenerife (Canary Islands, Spain) relies on basalt-hosted aquifers to provide 90% of water for agriculture and human consumption. The island is characterised by a low-permeability core, overlain by permeable materials which are cut by impermeable dykes. The effect is a compartmentalised aquifer, which is exploited sequentially as each “pocket” of water is exhausted. The island is home to ~1 million people (with an additional 5 million visiting tourists per year), and although rain/snowfall can be heavy in winter storms, it is unpredictable from year to year, and rapid surface water run off occurs due to the steep geography. While net recharge into the upper zones of the Tenerife aquifer have been quantified (around 2 months between intense rainfall and water table fluctuations), water must then follow a tortuous path to recharge lower zones and aquifer “pockets”. Water recharge to the coastal aquifers is also interrupted and extracted during its journey. Human and agricultural pressure is highest near the coast, and has led to intensive exploitation of existing wells and horizontal galleries. In response to the intensification of water extraction and slow recharge rates, marine intrusions into the coastal aquifers of Tenerife have occurred, traditionally recorded by rising chloride levels and resulting in well/gallery closures as well as increased pressure on other extraction sites. However, in a volcanic ocean island setting, natural processes can mimic the appearance of salinisation in a coastal aquifer. Management of aquifer resources require careful consideration of seawater incursions vs. volcanic degassing contributions vs. ocean island rainfall. Full hydrochemical breakdown of 43 coastal aquifer extraction sites reveal seawater intrusion is affecting the western coastal aquifer, with the agreement of multiple parameters. The strontium isotopic signature of well samples was also measured, because it is not subject to the biological or physical fractionation processes of other isotopic systems, thereby forming distinct reservoirs for groundwater (<sup>87</sup>Sr/<sup>86</sup>Sr of host rock), and seawater. <sup>87</sup>Sr/<sup>86</sup>Sr signatures suggest the northern coastal aquifers are also subject to seawater incursions. This parameter may be a more sensitive indicator than chlorides and conductivity markers for salinisation, especially in an ocean island environment where coastal aquifers are subject to intensive land use practices, seawater spray, and affected by diffuse volcanic degassing.</p>

Physical fractionation of organic carbon in areas under different land uses in the Cerrado

ABSTRACT With the expansion of agricultural production, native Cerrado areas are replaced with other forms of land use. Thus, the objective of this study was to evaluate changes in the physical fractionation of organic carbon (C) in areas under different forms of land use in the Cerrado. The treatments, with five repetitions, corresponded to the following forms of use: area under conventional tillage, area under pasture plantation, area under eucalyptus plantation and area under native Cerrado vegetation, at the depths of 0-5, 5-10, 10-15 and 15-20 cm in the municipality of Luis Eduardo Magalhães, BA, Brazil. The highest C contents and stocks were found in the eucalyptus area, which were equal to those of the area under native Cerrado vegetation, while particulate C stocks were higher in the area under pasture at the depth up to 10 cm, not differing from the area under native Cerrado. Pasture and eucalyptus had positive effect on C management index, regardless of depth.

A Comparison of Physical Soil Organic Matter Fractionation Methods for Amended Soils

Selecting a suitable physical fractionation method, to investigate soil organic matter dynamics, from the plethora that are available is a difficult task. Using five different physical fractionation methods, on soils either nontreated or with a history of amendment with a range of exogenous organic matter inputs (Irish moss peat; composted horse manure; garden compost) and a resulting range of carbon contents (6.8 to 22.2%), we show that method selection had a significant impact on both the total C recovered and the distribution of the recovered C between unprotected, physically protected, or chemically protected conceptual pools. These between-method differences most likely resulted from the following: (i) variation in the methodological fractions obtained (i.e., distinguishing between aggregate size classes); (ii) their subsequent designation to conceptual pools (e.g., protected versus unprotected); and (iii) the procedures used in sample pretreatment and subsequent aggregate dispersion and fractionation steps. The performance of each method also varied depending on the amendment in question. The findings emphasise the need for an understanding of the nature of the soil samples under investigation, and the stabilisation mechanism of interest, both prior to method selection and when comparing and interpreting findings from literature studies using different fractionation methods.

Organic matter and soil aggregation in agricultural systems with different adoption times

In conservation management systems, such as no-till (NT), it is important to analyze the pattern of changes in soil quality as a function of the time since adoption of the system. This study evaluated the physical fractions of organic matter and soil aggregation in management systems in areas cultivated with different times since implementation of NT: 6, 14, and 22 successive years of soybean and maize/wheat crops (NT6, NT14, and NT22, respectively); 12 years of no-till with successive years of soybean and maize/wheat crops, and the last 4 years with integration of maize and ruzi grass (Brachiaria ruziziensis) - (NT+B); pasture; and forest. Physical fractionation of organic matter determined the total carbon (TC), particulate organic matter (POM), and mineral organic matter (MOM) by calculating the carbon management index (CMI) and variables related to soil structural stability. Forest and pasture areas showed the highest contents of TC, POM, and MOM, as well as higher stocks of POM and MOM. Among the cultivated areas, higher TC and particulate fractions of organic matter and the best CMI values were observed in the area of NT22. There were changes in aggregation indices, depending on the time since implementation of NT. Areas of NT22, pasture, and forest showed the greatest evolution in C-CO2, indicating increased biological activity, with positive effects on soil structural stability.