To automatically install bower and its components, one must

1. Specify the bower dependency in package.json:

   "dependencies": {
       "bower": "^1.7.9"
   }
   

2. Use scripts to execute a postinstall command

   "scripts": {
       "postinstall": "./node_modules/bower/bin/bower install"
   }
   

3. Create a .bowerrc file to set the directory for bower_components to install. Otherwise bower_components are installed in root directory.

   {
       "directory" : "app/bower_components"
   }
   

Now, Heroku automatically executes bower install command after npm install