Nearly every plausible emission scenario that limits climate change to less than 2 °C includes net negative global emissions in the late 21st century. These negative emissions are achieved using negative emission technologies (NETs), a diverse class of currently theoretical technologies that use energy to remove CO2 from the atmosphere. While a number of technological options are available, many of the most promising CO2 capture systems take advantage of biological systems and are thus driven by light energy. Sulfur offers an alternative energy source for biological carbon capture. Herein, system models are presented that use reduced sulfur to power marine chemosynthetic carbon capture, with four proposed alternatives for the management of the produced biomass and sulfate. These four alternatives differ in the energy and process used to reduce the sulfate produced by the growth of the microorganisms back to sulfur or sulfide and in sum, the four systems create direct air carbon capture systems that utilize either geologic reduced sulfur, electricity, or biomass as energy sources. Thus, three new energy sources for direct air carbon capture are identified.