Fly ash from biomass gasification differs considerably from conventional combustion ashes. Gasification ash might contain high concentrations of unburned carbon and harmful, soluble compounds. This restricts direct ash utilization and makes some pretreatment necessary, representing a significant share of the overall operating cost of gasification-based systems for energy production. Therefore, economic methods for the management of this type of ash without any pretreatment are attractive. In this paper, we present an initial study on new lightweight plasterboard made of gasification ash. Our goal was to come up with a product that satisfies two basic requirements: (1) the product is mostly made of fly ash, and (2) the product enables the utilization of ash without any pretreatment. We manufactured plates by means of low-cost moulding and curing methods, using ash percentages of up to 60% (w/w). Gypsum and additives (vermiculite and fiber) were added to provide the plates with acceptable mechanical and thermal properties. The fly ash used was generated in a fluidized-bed pilot plant for processing orujillo, a byproduct of the olive oil industry. Mechanical, thermal, and environmental properties of ash gasification plates were studied and compared with commercial plates. The results lead us to conclude that the plates could be used commercially as fire-resistant construction boards, and therefore, the potential for commercial development is promising. In addition, the overall environmental benefit of waste gasification plus ash utilization of a difficult fly ash makes the overall process attractive.