Increasing Complexity Leads to Declining Productivity of Innovation in the Algal Biofuel Industry (Supplemental Information)

Liquid biofuels are widely promoted as renewable, lower-emission alternatives to fossil fuels. Yet despite their promise, this sector faces a critical constraint: a long-term decline in the productivity of innovation. This decline—measured by a decreasing number of patents per inventor—suggests that generating technological breakthroughs is becoming more difficult, expensive, and uncertain. As innovation becomes more resource-intensive, the feasibility of replacing petroleum with liquid biofuels grows more tenuous. This is especially problematic given the pre-existing technical disadvantages of biofuels, including their relatively low energy return on energy investment (EROEI) and energy density compared to fossil fuels. Our findings show that the innovation system supporting biofuel development is not scaling efficiently. Instead, it is approaching or may have already passed a point of diminishing returns.