Integrated biorefineries combine an assortment of existing technologies including those discussed earlier and other novel ones to convert biomass into biofuels, high-value bio­products, as well as heat and power. The idea behind an integrated biorefinery is to be able to produce a variety of high-value products as efficiently as the current petrochemical industry. Within the integrated biorefinery, heat and electricity are produced through con­version technologies, then used to produce high-value products, recycled to aid conversion, or sold on the commercial market (Figure 3.4). To be feasible, an integrated biorefinery must overcome a variety of challenges, including diversity of feedstocks, sustainability, and economic viability. Currently, pilot-, demonstration — and commercial-scale integrated biorefineries are operating in the United States [29].

The concept of integrated refineries has been implemented within the petroleum industry for many years. A typical oil refinery is capable of producing a variety of products, ranging from liquid petroleum gas, gasoline, jet and diesel fuels, wax, lubricants, bitumen, and petrochemicals, from which it manages production to maximize profit. This same concept also applies to integrated biorefineries. By producing a variety of products, the integrated

bioreflnery could help support a marginally viable biofuel market until it matures. The difficulties with an integrated biorefinery include guaranteeing a sustainable biomass supply that matches the desired product stream at a reasonable price. As the demand for biomass increases, the cost of acquiring material will likely increase, thus increasing pressure on the entire bioenergy industry.