NOVELTY - Thermolysis process for treating algal biomass comprising dried algal cells, comprises heating algal biomass from ambient to 460 degrees C in flowing stream that contains carbon dioxide, acetic acid, and/or other organic acids and that produces condensable hydrocarbon product whose mass yield is greater than the dry, ash-free mass fraction of lipids in starting algal biomass and whose higher enthalpy of combustion exceeds 25 MJ/kg plus a char, and hydrocarbon-laden gaseous product; or intimately mixing algal biomass with solid acid catalyst and heating from ambient to 460 degrees C in flowing gas stream.    USE - The thermolysis process is for treating algal biomass comprising dried algal cells, to obtain condensable hydrocarbon product plus a char, and a hydrocarbon-laden gaseous product (claimed). It is useful for the production of fuels, chemicals, and soil amendments, or to obtain products, i.e. new oily material that exhibits many of the characteristics of crude petroleum, and an aqueous stream that dissolves polar compounds.    ADVANTAGE - The process obtains feed stocks from which to prepare liquid fuels from renewable source, such as algal biomass that grows rapidly, with little impact on available water or food resources. It converts biomass comprising whole, dry algae cells, into an oily material that exhibits a heating value approximating that of petroleum. The algal biomass can be processed into the feedstock with a net decrease in carbon dioxide emissions, e.g. by using carbon dioxide and heat from an existing process that would otherwise be wasted. The process produces significant quantities of oily product from algal biomass that does not contain high concentrations of lipids. It is suitable even to algal biomass that has not been selected or nurtured to generate lipids. The thermolysis process produces a range of products that commence to evolve at unexpectedly low temperatures, i.e. as low as 50 degrees C, which is hundreds of degrees lower than the temperatures at which cellulosic biomass must be heated to produce pyrolysis oils. The temperature range of the thermolysis of the algal biomass is low enough that the process can be carried out using waste heat generated by other industrial processes, e.g. cement manufacturing. The low temperature processing confers an economic advantage and offers a possible route to carbon credits for the partner industry. The oily material derived from the algae has an unexpectedly high enthalpy of combustion, i.e. 36 MJ/kg, which approaches the heating value of petroleum ( approximately 44 MJ/kg) and is about twice as large as the heating value of pyrolysis oils derived from cellulosic biomass ( approximately 20 MJ/kg). The algal biomass-derived oily material can constitute more than 15 wt.% of the original, ash-free, dry weight of the algae, even for starting material that contains less than 5 wt.% lipids. The composition of the algal biomass-derived oily material makes it amenable to subsequent processing along side conventional petroleum-derived gas oil, unlike pyrolysis oils derived from cellulosic biomass. The oily material from the thermolysis of algal biomass presents fewer oxygen-containing components than the cellulose-derived pyrolysis oil, along with a concentration of sulfur that is low enough to be considered for blending into low sulfur feed stocks, yet high enough to maintain the activity of conventional hydroprocessing catalysts.