The invention provides an improved method of collecting biogas from a landfill that results in more complete collection of biogas produced in the landfill, and with less contamination with air. The method involves providing the landfill with an upper gas containment layer near the surface of the landfill to retard biogas escape and air entrainment into the landfill. Underneath the gas containment layer is provided a gas-permeable conductive layer. Underneath the conductive layer, a well withdraws biogas from the landfill. Withdrawal of biogas from the well creates a partial vacuum that draws gas from the gas-permeable conductive layer down through the waste mass to the well. If the rate of gas withdrawal from the well is too rapid, air will be entrained from the atmosphere into the gas-permeable conductive layer. But if the rate of gas withdrawal from the well is too slow, biogas may percolate through the gas-containment layer and the surface of the landfill to escape. Monitoring the gas composition of the gas-permeable layer allows one to determine quickly and continuously whether the rate of gas withdrawal from the well is too fast or too slow.