How to Backup/Restore Managed Metadata from one farm/environment to another

What?
SharePoint 2010 -2013 How to Backup/Restore Managed Metadata from one farm/environment to another?

Why?
You will be amazed by the lack of proper import/export functionality.
It is quite a general requirement to migrate Managed Metadata Service / Termsets from one environment to the other.

There are a few approaches to backup/restore managed metadata between environments.
OOB, SharePoint 2010 allows for ONLY importing managed metadata in CSV format. You are required to use Powershell / Object Model to build the csv file. Here is a script that can do it. Managed metadata terms and termsets each have a unique guid. If you take a backup of a site that is using managed metadata in some columns and restore this site into another environment, the guids don't match up. You will have to go through and re click each term and "wire it back up" so it's okay and doesn't show in red text. Paul Culmsee did a good job of explaining the same with nice screenshots here. This is quite hectic especially if there is a lot of data.

How?
The easiest and the effective approach is to LIFT the managed metadata service application from one environment to the other. That way you can ensure that the guids of terms and termsets match.
This process is done in PowerShell and involves exporting managed metadata service application first, then importing it in the target environment/farm.
Powershell Configuration:
Open PowerShell. You might get an error. “The local farm is not accessible”
If the farm admin account is used, this error won’t show up.
Make sure that the account that is used for deploying solutions / executing Powershell scripts has the following role memberships for SharePoint Config Database:

• public
• SharePoint_Shell_Access
• db_owner

Powershell for Export:

$mmsApp = “4a867ce5-d9ee-4051-8e73-c5eca4158bcd”; #this sets the exporting MMS ID

$mmsproxy = Get-SPServiceApplicationProxy | ?{$_.TypeName -eq "ExportTaxonomyProxyName"};

Export-SPMetadataWebServicePartitionData -Identity $mmsApp -ServiceProxy $mmsproxy -Path \\location\exportfile.bak;

mmsApp:

Navigate to CA > Application Management > Manage Service Applications > Managed Metadata Service Application

#Import 

$mms2 = "d045d3ce-e947-4465-b039-0dfbbe24fb22"   #this sets the importing MMS ID 

$mms2proxy = Get-SPServiceApplicationProxy | ?{$_.TypeName -eq "ImportTaxonomyProxyName"};

Import-SPMetadataWebServicePartitionData -Identity $mms2 -ServiceProxy $mms2proxy -path \\location\exportfile.bak -OverwriteExisting;

Fuente: 

http://underthehood.ironworks.com/2011/10/sharepoint-2010-how-to-backuprestore-managed-metadata-from-one-farmenvironment-to-another.html

https://blogs.msdn.microsoft.com/taj/2011/01/11/site-collection-backuprestore-and-managed-metadata/