I found this in the answer by Jason to this question http://stackoverflow.com/questions/19206764/how-can-i-load-activerecord-database-tasks-on-a-ruby-project-outside-rails. This is a Rakefile for using ActiveRecord without Rails. It loads ActiveRecord's databases.rake file making ActiveRecord rake tasks available for your non-rails app.

Rakefile.rb

require 'bundler/setup'

require 'active_record'

include ActiveRecord::Tasks

class Seeder
  def initialize(seed_file)
    @seed_file = seed_file
  end

  def load_seed
    raise "Seed file '#{@seed_file}' does not exist" unless File.file?(@seed_file)
    load @seed_file
  end
end


root = File.expand_path '..', __FILE__
DatabaseTasks.env = ENV['ENV'] || 'development'
DatabaseTasks.database_configuration = YAML.load(File.read(File.join(root, 'config/database.yml')))
DatabaseTasks.db_dir = File.join root, 'db'
DatabaseTasks.fixtures_path = File.join root, 'test/fixtures'
DatabaseTasks.migrations_paths = [File.join(DatabaseTasks.db_dir, 'migrate')]
DatabaseTasks.seed_loader = Seeder.new File.join(DatabaseTasks.db_dir, 'seeds.rb')
DatabaseTasks.root = root

task :environment do
  ActiveRecord::Base.configurations = DatabaseTasks.database_configuration
  ActiveRecord::Base.establish_connection DatabaseTasks.env.to_sym
end

load 'active_record/railties/databases.rake'