Evaluation of nutritive value and in vitro rumen fermentation gas accumulation of de-oiled algal residues

Background：Algae are widely recognized for their high oil content and for exponentially accumulating biomass with particular potential to provide single cell protein for human consumption or animal feed.It is believed that along with biodiesel from algae,the high protein de-oiled algal residue may become an alternative feed supplement option in the future.This study was conducted to investigate de-oiled algal residue obtained from the common Chlorella species,Thalassiosira weissflogii,Selenarstrum capricornutum,Scenedesmus sp.,and Scenedesmus dimorphus for assessment as potential feed supplements for ruminants by comparing with soybean（Glycine max） meal and alfalfa（Medicago sativa） hay.Results：With the exception of T.weissflogii,algal residue had higher concentrations of Cu,Zn,and Mn and lower concentration of Ca,Mg,and K than soybean meal and alfalfa hay.The algal residue CP（crude protein）concentrations ranged from 140 to 445 g/kg DM and varied among the de-oiled residues.In vitro rumen fermentation gas accumulation curves indicated that algal biomass degradation potential was less than that of soybean meal or alfalfa hay by up to 41.7%.The gas production curve,interpreted with a dual pool logistic model,confirmed that the fraction sizes for fast fermenting and slow fermenting of de-oiled algal residues were smaller than those in soybean meal and alfalfa hay,and the fermenting rate of the fractions was also low.Conclusions：Inferior in vitro rumen gas accumulation from the five de-oiled algal residues suggests that these algal byproducts are less degradable in the rumen.

Revolutions in algal biochar for different applications:State-of-the-art techniques and future scenarios

Algae are potential feedstock for the production of bioenergy and valuable chemicals.After the extraction of specific value-added products,algal residues can be further conve rted into biogas,biofuel,and biochar through various thermochemical treatments such as conventional pyrolysis,microwave pyrolysis,hydrothermal conversion,and torrefaction.The compositions and physicochemical characteristics of algal biochar that dete rmine the subsequent applications are compre hensively discussed.Algal biochar carbonized at high-temperature showed remarkable performance for use as supercapacitors,CO_(2) adsorbents,and persulfate activation,due to its graphitic carbon structure,high electron transport,and specific surface area.The algal biochar produced by pyrolysis at mode rate-temperature exhibits high performance for adsorption of pollutants due to combination of miscellaneous functional groups and po rous structures,whereas coal fuel can be obtained fro m algae via torrefaction by pyrolysis at relatively low-tempe rature.The aim of this review is to study the production of algal biochar in a cost-effective and environmental-friendly method and to reduce the environmental pollution associated with bioenergy generation.achieving zero emission enerev production.