heroku でnattoを使用したい。

ローカル環境では動いているnattoがherokuでは動きません。
チェックをしてもローカル環境と出てくるものが一緒なのでどこでミスをしているのかも把握できていない状態です。
どうかアドバイスをお願い致します。

調べて行った設定。
デプロイは出来てます。
bundleを使ってgem 'natto'を設定してます。

heroku config:set BUILDPACK_URL=https://github.com/diasks2/heroku-buildpack-mecab.git
heroku config:add LD_LIBRARY_PATH=app/.linuxbrew/lib
heroku config:set MECAB_PATH=app/.linuxbrew/lib/libmecab.so.2

公式のGithubをみて、どこに追記すればよいか分からなかったのでとりあえず、下の箇所に入れてみた。

//application.rb
class Application < Rails::Application
  ENV['MECAB_PATH']='app/.linuxbrew/lib/libmecab.so.2'

Natto::MeCabError (Could not initialize Model with options: '--node-format=%f[7]')

heroku run rails c
読み込めてない？？

Natto::MeCab.new
=> atto::MeCabError: Could not initialize Model with options: ''

Natto::MeCab.new('-F%f[7]')
=> Natto::MeCabError: Could not initialize Model with options: '--node-format=%f[7]'

ローカル　rails c
こっちではNatto::MeCab.newはちゃんと動く。

Natto::MeCab.new
=> #<Natto::MeCab:0x00007f881000af10 @model...

ファイルチェックしてみました。
find /app/ -name *mecab*

/app/.linuxbrew/Cellar/mecab-ipadic
/app/.linuxbrew/Cellar/mecab-ipadic/2.7.0-20070801/lib/mecab
/app/.linuxbrew/Cellar/mecab-ipadic/2.7.0-20070801/.brew/mecab-ipadic.rb
/app/.linuxbrew/Cellar/mecab
/app/.linuxbrew/Cellar/mecab/0.996/share/man/man1/mecab.1
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab/mecab-test-gen
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab/mecab-dict-gen
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab/mecab-system-eval
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab/mecab-dict-index
/app/.linuxbrew/Cellar/mecab/0.996/libexec/mecab/mecab-cost-train
/app/.linuxbrew/Cellar/mecab/0.996/lib/libmecab.so
/app/.linuxbrew/Cellar/mecab/0.996/lib/libmecab.so.2.0.0
/app/.linuxbrew/Cellar/mecab/0.996/lib/libmecab.a
/app/.linuxbrew/Cellar/mecab/0.996/lib/libmecab.so.2
/app/.linuxbrew/Cellar/mecab/0.996/.brew/mecab.rb
/app/.linuxbrew/Cellar/mecab/0.996/include/mecab.h
/app/.linuxbrew/Cellar/mecab/0.996/bin/mecab
/app/.linuxbrew/Cellar/mecab/0.996/bin/mecab-config
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-ko.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-ipadic.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-ko-dic.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-jumandic.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-unidic.rb
/app/.linuxbrew/Library/Taps/homebrew/homebrew-core/Formula/mecab-unidic-extended.rb
/app/.linuxbrew/share/man/man1/mecab.1
/app/.linuxbrew/var/homebrew/locks/mecab.formula.lock
/app/.linuxbrew/var/homebrew/locks/a3da242228cf276ea0b7776960145ae549f7ff3985e0ea873d7c145f4fbf9650--mecab-ipadic-2.7.0-20070801.x86_64_linux.bottle.tar.gz.incomplete.lock
/app/.linuxbrew/var/homebrew/linked/mecab-ipadic
/app/.linuxbrew/var/homebrew/linked/mecab
/app/.linuxbrew/etc/mecabrc
/app/.linuxbrew/lib/libmecab.so
/app/.linuxbrew/lib/libmecab.so.2.0.0
/app/.linuxbrew/lib/mecab
/app/.linuxbrew/lib/libmecab.a
/app/.linuxbrew/lib/libmecab.so.2
/app/.linuxbrew/include/mecab.h
/app/.linuxbrew/bin/mecab
/app/.linuxbrew/bin/mecab-config
/app/.linuxbrew/opt/mecab-ipadic
/app/.linuxbrew/opt/mecab
/app/app/.linuxbrew/lib/libmecab.so.2