NOVELTY - Producing a predetermined hydrocarbon product (I), from a primary Arundo donax feedstock, comprises: providing the feedstock with a water content; indirectly heating the feedstock in absence of oxygen to produce a gas stream and solids; cleaning the gas stream and removing carbon dioxide and solids; determining the amount of carbon monoxide and hydrogen; partially oxidizing the secondary feedstock to produce heat; and comparing the percentage of carbon monoxide and hydrogen with the desired carbon monoxide and hydrogen to produce the predetermined (I).    USE - The process is useful in the production of predetermined hydrocarbon products, which are methanol, ethanol or alcohols, aldehydes, ketones, carboxylic acids, esters or other oxygenated hydrocarbon derivative (claimed) and biofuels and which are useful for e.g. internal combustion engines.    ADVANTAGE - The process provides increased ethanol produced per acre of biomass, reduced input-energy needs and reduced unwanted by products. The process provides better efficiency and lower use of fossil fuels than traditional commercial processes. The process does not use any fossil fuel on an ongoing basic to provide thermal energy to conduct the gasification process.    DETAILED DESCRIPTION - Producing a predetermined hydrocarbon product of formula (CxHyOz) (I), from a primary Arundo donax feedstock comprising substantially only Arundo donax as a carbon source supplemented by a secondary feedstock, comprises: providing the primary Arundo donax feedstock with a water content of not greater than 25%; indirectly heating the primary Arundo donax feedstock generally in absence of oxygen to produce a gas stream and solids; cleaning the gas stream and removing carbon dioxide and solids to produce a cleaned gas stream; determining the amount of carbon monoxide and hydrogen in the cleaned gas stream; partially oxidizing the secondary feedstock to produce heat for the indirect heating of the primary Arundo donax feedstock and to produce a secondary gas stream, where the secondary feedstock is selected based on determining the heat desired to indirectly heat the primary Arundo donax feedstock, comparing the percentage of carbon monoxide and hydrogen in the cleaned gas stream with the desired carbon monoxide and hydrogen to produce the predetermined (I) and determining an additional amount of carbon monoxide and hydrogen desired from the secondary feedstock then determining the secondary feedstock, and where the process further comprises calculating the amount of carbon monoxide, hydrogen and heat to be produced from the secondary feedstock; combining the carbon monoxide and hydrogen from the cleaned gas stream with the secondary feedstock gas stream to produce a mixed gas stream; providing a catalyst for the mixed gas stream to produce a predetermined (I) gas; and distilling the predetermined (I) gas to produce the predetermined (I).    X, Y1, Z = integers.    An INDEPENDENT CLAIM is included for designing a plant for producing a predetermined (I), comprising determining the heat required to indirectly heat the primary Arundo donax feedstock, comparing the percentage of carbon monoxide and hydrogen in the cleaned gas stream with the required carbon monoxide and hydrogen to produce the predetermined (I) product and determining the additional of carbon monoxide and hydrogen required from the secondary feedstock, determining the secondary feedstock, and calculating the amount of carbon monoxide, hydrogen and heat to be produced from the secondary feedstock.