Gasification is a promising technology for the conversion of mixed solid waste like refuse-derived fuel (RDF) and municipal solid waste (MSW) into a valuable gas consisting of H₂, CO, CH₄ and CO₂. This work aims to identify the basic challenges of a single-stage batch gasification system related to tar and wax content in the producer gas. RDF was first gasified in a simple semi-batch laboratory-scale gasification reactor. A significant yield of tars and waxes was received in the produced gas. Waxes were analyzed using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectrometry. These analyses indicated the presence of polyethylene and polypropylene chains. The maximum content of H₂ and CO was measured 500 sec after the start of the process. In a second series of experiments, a secondary catalytic stage with an Ni-doped clay catalyst was installed. In the two-stage catalytic process, no waxes were captured in isopropanol and the total tar content decreased by approximately 90 %. A single one-stage semi-batch gasification system is not suitable for RDF gasification; a large fraction of tar and waxes can be generated which can cause fouling in downstream processes. A secondary catalytic stage can significantly reduce the tar content in gas.

The genus Allochrusa (Caryophyllaceae) comprises nine species, which are native to Central Asia, Turkey, Iran, Afghanistan, and the Caucasus. They have been used in folk medicine and in the preparation of various sweets and detergents, especially in Asian countries. A diversity of secondary metabolites has been reported from the genus Allochrusa, including triterpene glycosides, ecdysteroids, flavonoids, volatile compounds, fatty acids, polysaccharides, pectins, hemicelluloses, and other phytochemicals. In vitro and in vivo pharmacological studies on isolated compound fractions and extracts from Allochrusa species showed anti-inflammatory, adjuvant, hemolytic, cytotoxic, antifungal, analgesic, antioxidant, and other activities. In this review, the chemical compounds and diverse biological activities of the Allochrusa genus are summarized.