• Create a custom Visualforce Page say Page1.
• Use the REST Tooling API (https://resources.docs.salesforce.com/sfdc/pdf/api_tooling.pdf)call using Apex code, to the following REST url endpoint to retrieve all the Workflow Rule info for the org

https://yourinstance.salesforce.com/services/data/v35.0/tooling/sobjects/workflowrule/describe

• Have another Visualforce page say Page 2, where the content type of the page is set as follows. You will need to ensure that the Workflow rule info to be passed over to Page2 for it to be displayed within an excel.

<apex:page controller="contactquery" contentType="application/vnd.ms-excel#SalesForceExport.xls" cache="true">
    <apex:pageBlock title="Export Results" >
        <apex:pageBlockTable value="{!cs}" var="contact">
            <apex:column value="{!contact.ID}"/>
            <apex:column value="{!contact.Name}"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:page>

• Using a Scheduled Job or Setup > Developer Console > Execute Anonymous populate the Workflow metadata info by querying the Tooling API REST endpoint shown in approach 1.
• Store the response in a custom object, lets say Workflow Metadata.
• Create a Custom Report on the Workflow Metadata object and then using the Eport as CSV option from Salesforce Report Builder to export the workflow metadata information within a CSV / Excel.