The invention present provides a method (and suitable apparatus) to convert biomass to ethanol, comprising gasifying the biomass to produce raw syngas; feeding the raw syngas to an acid-gas removal unit to remove at least some CO.sub.2 and produce a conditioned syngas stream; feeding the conditioned syngas stream to a fermentor to biologically convert the syngas to ethanol; capturing a tail gas from an exit of the fermentor, wherein the tail gas comprises at least CO.sub.2 and unconverted CO or H.sub.2; and recycling a first portion of the tail gas to the fermentor and/or a second portion of the tail gas to the acid-gas removal unit. This invention allows for increased syngas conversion to ethanol, improved process efficiency, and better overall biorefinery economics for conversion of biomass to ethanol.

Microorganisms and bioprocesses are provided that convert gaseous substrates, such as renewable H.sub.2 and waste CO.sub.2 producer gas, or syngas into high-protein biomass that may be used directly for human nutrition, or as a nutrient for plants, fungi, or other microorganisms, or as a source of soil carbon, nitrogen, and other mineral nutrients. Renewable H.sub.2 used in the processes described herein may be generated by electrolysis using solar or wind power. Producer gas used in the processes described herein may be derived from sources that include gasification of waste feedstock and/or biomass residue, waste gas from industrial processes, or natural gas, biogas, or landfill gas.

A system for high-value utilization of organic solid waste includes an anaerobic digestion unit, a biogas measurement and collection unit and a methane purification and liquefaction unit. The anaerobic digestion unit includes an organic solid waste pretreatment system and an anaerobic digestion device. The biogas measurement and collection unit includes a gas flow meter and a high-pressure biogas collection device. The methane purification and liquefaction unit includes a high-pressure separation tank, a liquefaction pretreatment system, a heavy hydrocarbon and benzene removal device, a two-stage rectification system, a low-temperature pressure liquid storage tank device and a buffer storage tank. The organic solid waste undergoes an anaerobic digestion treatment to produce methane followed by collection, purification and liquefaction.

Disclosed is an absorbent containing an amine for absorption of an acid gas in a biogas, and a biogas purification system using the same.

The invention relates to a method for membrane permeation of a gas flow including methane and carbon dioxide, wherein said gas flow is cooled to a temperature of 0° C. to −60° C. before being fed into a membrane separation unit.

Disclosed is an adsorbent containing a metal oxide for adsorption of hydrogen sulfide in biogas, and a biogas purification system using the same.

A technique to desalinate seawater using melanin-concentrated solar energy wherein the melanin is extracted from a local isolate Aspergillus niger. A device consists of two fixed upper and lower containers with same volume of seawater in both, with or without melanin powder dissolved in the lower container at rate of 0.17 gm of melanin powder per 10 ml of water. The device is put outdoors under direct sunlight during daytime, circular water droplets free of salt starts to appear on the external bottom of upper container. Water droplets are collected by a sterile glass rod, pH of droplets water is about 7.1. Yield of fresh water is approximately 10 ml droplets water from 600 ml seawater per hour; after 24 hours day and night incubation, seawater in the upper container dries out leaving salt crystals. Yield of 1000 m3 seawater is 100 m3 freshwater (1000 L seawater yield 100 L freshwater).

Embodiments of the present disclosure describe bioreactor systems that integrate phototrophic organism cultivation with energy harvesting, methods of using said bioreactor systems, and the like. The bioreactor systems can comprise a bioreactor, wherein the bioreactor is configured to cultivate a phototrophic organism in a liquid growth medium, and at least one transparent photovoltaic panel positioned between the bioreactor and a light source, where the transparent photovoltaic panel transmits select wavelengths of light and absorbs select wavelengths of light.

An anaerobic digestion system is provided. The system includes a biomass storage container and a cover positioned over the biomass storage container, where the cover is sealed at an outer edge of the anaerobic digester. Weights may be arranged on the surface of the cover, and the sealed edges may form a water collection region. Additional systems, including thermal management, gas processing, energy storage and recovery, and sensing can also be included.

Provided is a method of capturing and recycling carbon dioxide from on-island combustion emissions using sustainable solar energized aquaculture of algae, including the steps of: generating electrical power from at least two renewable power producing systems, wherein the renewable power producing systems comprise at least a solar photovoltaic cell and a water turbine; and storing the electrical power in a battery array.