Green Patent Acquisitions: Rentech Buys SilvaGas Gasification Technologies


Rentech, Inc. (Rentech) is a Los Angeles company that provides clean energy solutions including biomass gasification technology and processes for converting synthetic gas (syngas) into synthetic jet fuel and diesel fuels.

Last month Rentech announced that it had completed the acquisition of Atlanta-based SilvaGas Corporation (SilvaGas) and SilvaGas’s commercial-scale biomass gasification technology, which converts urban waste feedstocks into syngas.

According to the press release, the acquisition will enable Rentech to offer integrated packages for renewable fuels and power production by combining the SilvaGas gasification technology with Rentech’s syngas conversion, conditioning and cleanup technology.


The SilvaGas patent portfolio includes several patents and pending applications relating to high-throughput gasifier technology.  The original SilvaGas process was protected by U.S. Patent No. 4,828,581 (‘581 patent), entitled “Low input gas velocity high throughput biomass gasifier”.  The ‘581 patent expired in 2006.

The ‘581 patent describes a process of rapidly heating biomass with hot sand using a reactor that has a fluid bed of sand.  According to the ‘581 patent:

This invention comprises the unexpected discovery that it is possible to gasify biomass at very high wood throughputs but in an entrained gasifier operating at low inlet gas velocities.

Entrained gasifiers perform gasification reactions in a cloud of fine particles, which can be solids, atomized liquid fuels or fuel slurries.

Another key SilvaGas patent is U.S. Patent No. 6,613,111 (‘111 patent), entitled “Small scale high throughput biomass gasification system and method”.  The ‘111 patent is directed to a high-throughput combination gasifier and combustor wherein the gasifier is concentrically housed within the combustor. 

The gasifier system includes a gasifier (102) and a combustor (118).  The combustor (118) acts as a source of heat to drive the gasification reactions in the gasifier (102).  The gasifier (102) and combustor (118) transfer heat and materials to each other via circulation of a particulate inert material, such as sand, which is fluidized by gas flowing through the material. 


A fluidizing gas inlet (110) provides a flow of gas into the gasifier (102), and gas exits the gasifier at exit (112), flows through a separator (114), and exits as product gas through product gas exit (116).  Biomass feedstock is introduced through the entry opening (106), and the particulate material travels from the combustor (118) into the gasifier (102) through a recirculation opening (108).

According to the ‘111 patent, the arrangement of the gasifier (102) concentrically within the combustor (102) minimizes heat loss from the surface of the gasifier and improves the efficiency of the system.  This helps to make the patented system suitable for small scale gasification having a relatively low feedstock input rate.

Most of the other SilvaGas patents and applications are directed to improvements or variations of these core technologies, including U.S. Patent No. 6,808,543 (methods for reducing ash agglomeration, reducing erosion and facilitating sand flow), U.S. Patent No. 6,680,137 (an energy system connecting a gasifier and a combustor to a fuel cell) and U.S. Application Pub. No. 2008/0022592 (a more efficient gasification system having certain diameter and height specs).

Eric Lane Avatar

Eric Lane

Eric Lane, the founder and principal of Green Patent Law, is an intellectual property lawyer and registered U.S. patent attorney in New York and is a member of the bar in New York and California. Eric has more than two decades of experience working with wind, solar PV, CSP, biofuels, and geothermal, energy storage technologies, carbon capture and sequestration, medical devices, data communications, mechanical, chemical, internet and software.