And, given the size of the legend for piechart(), you will have to use a vertical orientation for the tiledlayout plots.
Costs = ["Feedstock","Chemicals","Labour","Maintenace",...
"Insurance and Taxes","Overheads","Waste Disposal/WWT","Utilities"];
Cost_Values1 = [13.7341 0.1162 1.0288 0.9720 0.9720 0.9760 0.2263 0.1162];
Cost_Values2 = [13.777 1.110 1.226 1.650 1.650 1.163 0.2829 0.11654];
tiledlayout(2,1)
nexttile
p1 = piechart(Cost_Values1, 'LegendVisible', 'on', 'FontSize', 10);
%Get the labales
Labels = p1.Labels;
%Change the names of the slices
p1.Names = Costs;
%Changing the names of the slices also changes the labels,
%And that makes things a bit packed/stuffed, so revert back the changes
p1.Labels = Labels;
title("BE-CHP")
nexttile
p2 = piechart(Cost_Values2, 'LegendVisible', 'on', 'FontSize', 10);
Labels = p1.Labels;
p2.Names = Costs;
p2.Labels = Labels;
title("BE-CHPCCS")
colororder meadow;
