Non-renewable resources are resources for which there is a limited supply. The supply comes from the Earth itself and, as it typically takes millions of years to develop, is finite. Non-renewable resources can generally be separated into two main categories; fossil fuels and nuclear fuels.
But there were pockets of the North on the eve of the Revolution where slaves played key roles in the economic and social order: New York City and northern New Jersey, rural Pennsylvania, and the shipping towns of Connecticut and Rhode Island.
In fact, prior to the Emancipation Proclamation captured slaves were returned to their masters by Union troops in Missouri, Kentucky, Delaware and Maryland and there are records of the Union Army conducting slave auctions, mostly in Kentucky, with slaves who escaped and were headed north when captured by the Union Army.