Setting environment variable within Nuget config

Question

I am trying to implement continuous integration with Bamboo for a .NET project which is using package-reference style. I have tried to set the globalPackagesFolder in NuGet.config the following way

<config>
    <add key="globalPackagesFolder" value="%ENVIRONMENT_VARIABLE%/NUGET_PACKAGES" />
</config>

The environment variable has been set on the system. When I trigger the bamboo build, it seems to download the packages to the application path this way

E:\bamboo\agent01\bamboo-agent-home\xml-data\build-dir\PRJEMRDV-EMMRDEVELOP-EMMRDEVELOPBUILD\Modules\%ENVIRONMENT_VARIABLE%\NUGET_PACKAGES

So I presume this needs to be set within Bamboo. Please correct me if I am wrong so is there any other issue?