Spent years around refinery projects, and the pattern is always the same: the engineering is rarely the reason a small-scale or modular refinery dies. It's one of three things:

1. Permitting sequencing — investors apply for the wrong permits in the wrong order and lose 6-12 months waiting on approvals that depended on approvals they hadn't started yet.

2. Capital structured for the wrong stage — raising construction-phase capital before feasibility is locked means investors get spooked by the first change order.

3. Feedstock contracts signed too early — locking supply before your throughput capacity is finalized leaves you either overpaying or short.

Modular refineries (5,000-30,000 bbl/day range) are genuinely viable right now for independent operators — the technology and financing options have both matured a lot. But the projects that make it to first barrel treat feasibility and permitting as the actual product, not a checkbox before the 'real' work starts.

If you're mapping out a project like this, happy to talk through what stage you're at.