Cumulative processes in multi-system transitions: expanding value chains and limits to growth for sustainable alternatives

• Longitudinal analysis of the evolution of biomethane in Sweden. • Linkage systems connect upstream and downstream systems in new value chains. • Niche accumulation in downstream systems comes with cumulative upstream processes. • Different systems follow distinct yet complementary transition pathways. • Raises critical questions about the limits to growth for sustainable alternatives. This paper examines the long-term evolution of biomethane in Sweden as a case of a multi-system transition, involving interactions across several sociotechnical systems over more than three decades. Biomethane is conceptualized as a linkage system that connects different systems through a new value chain configuration. The analysis shows that additional systems were gradually incorporated, leading to a continuous expansion of the value chain. While the overall transition is characterized by cross-system reconfiguration, the individual systems exhibit distinct yet complementary transition pathways, including new system emergence, transformation, and substitution. The paper argues that the niche accumulation associated with substitution in downstream systems must be accompanied by cumulative processes in upstream systems to meet increasing demand. This expansion has important implications for sustainability assessments. The paper concludes that cumulative growth in expanding value chains raises critical questions regarding resource availability and limits to growth for sustainable alternatives.